LP ‘ Ht tet 4 Arita HHH HEHE Catal tgieretentets rH HH fetate tel regtylgtely HHH HM HHL ttt tate AHHH HM PH terete tie H Ht ate tit t $ 4H io Be \ 5 f 7 b R : i} sued tt eae eet re ga H Ht Ane Hitaly t Lite Guntyh t HHH HHH Heese Vet En te rete inte eeerepea recat reget eet eteet ety ltt teat rH ree tte e et tet gt iterate! eet treater RR CRE at tity i it HH itt i ie Sa ey tghytet THM ey Pe HM ey THE eh tity Hal sgtytety RHR HH tert ylyty tt Re HHH Cot Lee t intel retegratet it HE eH | — i a Cte reel lglg tpt reneterty eect ert a ttyl ut HH 4, fet it fel i Hie cere iu cc ee ee ee A Lay YES cl AY Si Ae GD cry ey tt =e Han RHO Cpiprate trey Hated gereest cent ela tety i HHH rh: iit Cottrte tgs i eitaty L} LH yi} ri i} Hh HH thylety sitet etety Cth HT cnet 1 eictety tia i Te . EH claret ietetetstalatete : HEHEHE TM ee Sette etsy rae eee if RHR HY - ¥" ~ SA nr ee ata : e “as! en Co ae oar £ -e ry 4 Contrived’&DladeinWletal Ivory rr Obfervations of Liutloso, ard ande eS eS) toby Tho" Neatha theHen We, CO M:ith Books of heir fet, eam, Ty Pie fle _ The New Lmproved Theodolte. The Double Level. : —— . i) = == SS ; ; . re = or ood accor Lng tothe lalestom = Practitioners of Wathematical net thee Tountuh my Sran.fondone Vath erratic ' ress or He PRACTICAL SURVEYOR: | eee CONTAINING | The moft approved Methods . FOR i "Surveying of Lanps and Wate BA By the feveral INSTRUMENTS NOW IN USE: Particularly exemplified with ‘The Common and New Theodolites, AND ALSO | How to plot and caft up fuch Surveys, wee the Manner of adorning the Maps thereof. To which ate added, Some ufes of the new Theodolite, viz. In drawing the perfpective Appearance of Buildings, €s’c. In levelling, for, the conducting of Water, and In taking the Dimenfions of ftanding Timber. Together with the Defcription and Ufe of An improved Sliding-Rule for Timber, ee, An Loker) Dial, ' A Meafuring Wheel, and The Pantographer, for copying of Drawings. Firft publifhed in part, By JOHN HAMMOND; Since enlarged, By SAMUEL WARNER; And now revifed, correfted, and greatly augmented. Ry me a a RET RE UN am “The THIRD EDITION. ie 0 aN DO Vv . ; Printed for T. Heatu, Mathematical-Inftrument-Maker, at the Hercules and Globe, near Exeter-Exchange in the Strand. “MDCCL. ao ¢ 2 Jy ed ah, pant “venieiy ( to eae t ' % - 4 cnt + byline She! ithe a) ria PREFACE N the following treatife is coritained the whole bufinefs of land furveying, in the manner.as 1S NOW practifed by the moft experienced artifts ; together with fuch problems and obfervations as are ‘really neceflary :, And herein the fubject is treated of in fuch a plain, tho’ concife manner, that the moft common Capacity, with a very little refleGtion, will readily conceive the whole ;, efpecially if hie has thie inftruments before him while he reads of their ufe: And although a great part of this work may be like what has been delivered by other writers, yet’ there is not one article relative to ptactice, but. what the authors have drawn from their own experience. The reader will hére find, after fome few intro- ductory problems, a very par ticular and exact deferip- tion of the feveral inftruments ufed in furveying, and’ a jut comparifon of them together ; ‘particularly the various forts of Theodolires: With due directions and cautions in their management, according to their feveral kinds; in order to prevent errors and mi- ftakes, as well in the taking obfervations, and core recting them on the fpot, as in plotting and laying them down in the draught. Alfo two very large examples, being parts of ac- tual furveys, containing moit of hers varieties that, can happen in the pradtife of this arc; the one per- formed by the common Théodolite, the other by the a new 4i Th PREFACE. new improved Theodolite: The manner of keeping the field-book in a diftinct and clear method is here fhewn; how the obfervations and meafures are to © be plotted, and the contents of the feveral inclofures _ and pieces caft up: Alfo in the courfe of thefe two examples, and other parts of the work, there will be met with, every caution and direction that can any way contribute towards the ready difpatch and ac- curacy of the practitioner, not only with regard to the field work and plotting, but alfo in the drawing, colouring, and ornamenting of the map. The new improved Theodolite is herein explained — in its parts and ufe ; alfo its application to water level- ling, taking of heights, and drawing in per/pective, are diftinctly and clearly treated of, In the account of the Meafuring-wheel, Univer- fal-dial, and Pantographer, the reader will fee fome particulars very ufeful and interefting; but, as there is annexed a copious table of contents, it will be necdlef$ in this place to infift further on any of the atticles contained therein. | The major part of this work was originally com- pofed by that ingenious artift Mr. Samuel Cunn ; but for fome reafons he let it appear under the name of Fobn Hammond, who was a clerk to his friend Mr. Charles Brent. ‘The fecond edition of this book was under the care of Mr. Samuel Warner, a perfon well known for. his fkill in the bufinefs of furveying; he added an appendix, containing a more particular de- feription of the Improved Theodolite, with a new method of ufing it in taking obfervations in the field ; whereby an error may be more readily difcovered and prevented than by any other way hitherto ufed ; with an example of the field-book of part of an ac- tual furvey taken thereby. Likewife a full explana- tion of the manner of laying down thofe obfervations from one center, fo as to avoid the faults which arife from protracting angle by angle. As alfo how to reduce ~ ae The- P. R: E- FACE; iit reduce irregular figures to triangles, with the appli- cation thereof in the cafting up the contents of the forementioned example. This appendix is now put into the body of the work, part being in Seétion I, and of the reft is compofed the VIIIth SeGion. | In the prefent edition, the former order of the fubjects are varied, the revifer thinking the order they now ap- pear in to be better: But befides this change, there are a very confiderable yariety of corrections, alter- ations, and additions; for the X1Vth and XVith Sections are not only added, but there ate introduced into the work, many articles not in the former edi- tions, and which were now thought very necellary to be communicated: Notwith{tanding which, the bulk of this book is not increafed above the former ; tho’ the prefent contains near three fheets of matter more than was in the laft ; \which has been effected by: making the page both broader andlonger. Alfo the figures which in the former impreffions were in four fmal] plates, indifferently defigned, and as ill refer- red to, are in this brought into one plate, and ren- ‘dered more ufeful. It may be proper to obferve, that fome of the no- tions in Section XIV were drawn from a little book of Martin Mafter, publifhed in 1661: And part of the XVIth Section, is a tranflation from a French piece publifhed by C. Langicis, an engineer to the French King, who pretends to no more than to have perfected an inftrument of this kind already known ; and, indeed, among the inftruments of Sir ‘fonas Moore, fuch a one was found, but fomewhat more antique and inconvenient than that which is now pro- pofed: But M. Langlois not having given a tab'e of the. lengths of the feveral divifions from their refpec- tive centers, nor how they are to be found, it was thought proper to add thefe articles to compleat th¢ account of the Pantographer. Feb. 18, FOR 1749-50. is 3 2 Note, iv Th PREFAC E: : Note. The enfuing directions having been jae in their proper places, it was thought convenient to annex them in this place. in the beginning of the field-book it will be pro- | per to write ore ach title as the following~ The field-book, containing obfervations and di- menfions taken in the furvey’ of the manor of. in the parifh of-——in the county of. ; belong- ing to Surveyed in the months af in the year-———by———-and the following affiftants, wiz. A. B. of the parifh of. labourer. Cp: mae &e. Specifying their names, places of abode and occu- pation 5 and at the beginning of each day, write the_ day’s name, day of the month and hour; alfo at the end of each day’s work write the hour ; and, if there fhould be occafion to change any of the aMiftants, or have new ones, let this be alfo inferted, with the day: For fuch obfervations may be of fervice, in cafe the furveyor fhould, on any account relating to the premifes, be called on to give his teftimony. In drawing out the Terrier “of a furvey, a difpo- fition, fomewhat like the following, may be found convenient. In fix columns, titled N°, Kind, Names, Proprietors, “Tenants, Quantity ; write 1ft, The number refered to in the map, if the fe- veral pieces therein are numbered. 2d, ‘Che kind, whether arable, pafture, meadow, wood, garden, Hautes! yards, water, EFe, gd, The name that the piece is known by. 4th, The name of the lord of the manor, or other perfon, to whom the piece belongs, whether in fee- fimple or copy-hold, 5th, The name of the tenant who rents, or oc- cupies the piece, 6th, The quantity that piece contains, in acres, rods, ent poles, eth ANE ALIEN I, op si dig: 8 085 4 SE. C yee B " F menfuration in general, with the moft necef- - O° fary geometrical problems. page 1 Viz. To draw perpendicular lines. at To bifeét lines. 4 Io make equal angles. | 5 To draw parallel lines. 5, 6 _ Lo divide right lines into many equal parts. 6 _ To make equal right lined figures. 7 To reduce irregular figures to triangles, 8 i Sy Ovo vir: Of bir uments ure in iH ieee of land. If Bee Peony. To obferve the ne tion of a line by any of the pre- ceding infiruments. 14 Pirft, By the circumferentor. . ibid. To try.if a needle plays well. 1s . Lo protratt any line, whofe bearing is taken | by the circumferentor, 17 Rerondlys To obferve with a Theodolite, both by the limb, and by the box and needle. 18 To corrett the angles and bearings, before the infrrument is removed, ~\19 T 0 plot, and therein to difcover and cor- \ rett an error before it is communicated to the following part of the work 25 Traverfe tables, ufeful in furveying. 28 Thirdly, To obferve with a femitircle, that has a box and needle. 30 Fourthly, Of the peraétor. ibid. Fifthly, Th CONTENTS. F ifthly,. Of the plain table, a = © Totake a plan by the plain table. 32 Sixthly, Of working with the chain. 35 Of the off-fet faff. ibid. and 52 Of the arrows. | ibid. ' Lo take the pofition of lines by tbe chain. 38 To plot uch pofitions. - 40 To find the pofition of a meridian line. 4t SlE iG. Bay, | To caft up the contents of land; with the method of reducing irregular curves to ftrait lines, 43 S. E.G Desi Of the laying out, or dividing of land 46 Firft, By a line parallel to one fide. v4 49 Secondly, By a line drawn frow one angle. 50 Thirdly, By lines drawn from any point within, 51 S: BE Gta VAR The ufe of the common Theodolite, exemplified in fur- veying of feveral parcels of land lying together ; with the form of a field-book. 52 How off-fets are to be taken. 3 54 To difcover errors caufed by the lofs of arrows. 56 To correct the obfervations of pofition. : Van To mark a flation, fo as to find it again, 61 Of the allowance for afcents and defcents, 65 Neceffary cautions, Pi 60 The field- book, 68 S.E.C: Ty. Vik To protrad the obfervations contained in the pre- ceding field- book: 87 To prevent errors in plotting. go What articles foould be inferted in plans. To make a fair plan from the rough draught. 94 SE Gabe Of a ncw, certain, and expeditious method of jur- veying and plotting by the Theodolite, as now improved. ) Os Caujes of the lines of a draught not clofing. ibid. | The oa aaa 5 ite - The GON-HEM TS St The improved Theodolite decribed, | 97 i boot with this Theodolite, : Pe book of part of an actual her pey performed a Oy this infirument. 102 ee the obfervations and meafures in this jfield- book are protratted. 112 The cafting up the contents of this furvey in fe- parate pieces, and in one, piece. | 116 RC We TR Of furveying of shoals and fands by help oF the new Theodeliie. 119, Soe A, Oe a> Of water levelling, or the condutting of water, 122 To adjuft the level. ibid. To ufe the level. . vig NBOe Neceffary obfervations. “4 226 Table of allowances for the curvature of the earth 128 Pil, Dyk Of colours and pencils. 130 S.E.C.T. -XIL A further ufe of the Theodolite (as now improved) ; conjointly with ibe ufe of a fliding-rule aptly divided; to meafure timber either round or hewn to a fquare, or unequally [quared: Alfa how to allow for afcents and defcents, by find- ing the horizontal lines. ¥23 Of the notation of the fiding rule. ibid. Io meafure planks. 133 To meafure round timber. 139 Lo meafure fquare timber. Se _ Lo meafure parallelopipeds. To meafure the height of ftanding timber by the Theodolite. 150 To find the horizontal lines in floping ground, 151 ShcG Te RI. The ufe of the Theodolite in drawing ihe per- fpcéiive appearance of any building without meafuring one fingle line. 152 b Firft, vill Fhe* C‘O-N* TE ON’ Ts: Virft, When the pitture is parallel to one of the fronts. yn os Neceffary theorems in pir oceans r55 Secondly, When the picture flands againf{ an | angle of the building, oblique to two - adjoining fronts. TS7. 5S aA ty | The defcription and ufe of the Perambulator, or Mea/uring-wheel, 159 To find the diftance run by the wheel, ‘160 — How this inftrument may be made to do the bufi- nels of furveying ee with its advan-— tages. 16 I/ $-B:C-T. ae , The defcription and ufe of the Univerfal Dial, hid of the variation of the compafs; 164 Of the pedeftal of the dial. , 165 Of tbe meridian, equinotital and bridge. 166 Ina known latitude, on a given day of the month, to find, Firft, The hour of the day. Lae se Secondly, The pofition of the meridian, 168 Thirdly, The pofition of the pole. | ibid, Fourthly, The variation of the needle. ibid, Fifthly, The Sun’s azimuth. ibid. sixthly, The Sun’s altitude. — ibid, Ta find the declination of a wall. ibid. To apply this dial to a Theadolite, gibt ys To find the latitude of a place by the common Theo- doliie. 171 Sof hee T. Sev 1 Lhe defcription and ufe of the Panera or Imitater, 173 — Toufe the Pantographer — 174 Of the different parts of the inftrument. 196 To compute the difiances of the div fe ons from their — relpeftive centres. 180 Eight plates. * . ~ * es - OS — cage — a ial ee steed nee ee sgh cal h a a es sa vii — 6c woke Sore - sal i Te me GEER eNO AR GA appli EERE S SAR LORS IE so Sa SESE SIS SCE a eae ante ee ne oe Se ee ee >i at Al Lee lee 5 2 | 1 SS Lh Ape GS “3 LD. : SD a c Nie l= ‘aaa one ‘e Joe 4 By 8423 JOG UE SE boa STOLOTOLOEO TS ok 80) BO EG O45 ES ros FE SOE Oe sop soe se PO RSS 7th Te ‘SB CoBeiol Of Mensur ation in general, with the moft necefjary GEOMETRICAL PROBLEMS. Geometricians ufe the word, is, to Wi? aflume any certain Quantity, and ex- WZ prefs the proportion which other fi- NW milar Quantities bear thereto: But IWeLA® in the common acceptation, to Mea- irc, is, to apply fome certain known quantity pitched upon for a ftandard, and thereby to determine the precife extent, quantity ot capacity of any thing of the fame kind. Thus: The meafure of a line is found by applying the lineal Inch, Foot, Yard, Pole, &@c. to that line, in ; B o.der | CHYy | order to difcover its length ; the doing of which is called Lougimetry. rs The Meafure of a fuperficies is obtained by the application of the fuperficial or fquare Inch, Foot, Yard, Pole, Acre, &%c. thereby to determine its Areaor Content; the method of doing which is called | Planimetry, whereof Surveying of land is a part ; and of this the following pages chiefly treat. ~~ ~ The Meafure of a Solid is had by comparing it with the folid or cubic Inch, Foot, Yard, Gallon, — €%c. thereby to find its capacity or folid content, ~ which is called Stereometry, and comprehends the meafuring of Timber, Stone, &c. Now, though it cannot be fuppofed that any Per- fon, who is wholly ignorant of the firft principles of Geometry, fhould expect to become a compleat Sur- veyor by barely reading this Book, whence it might. feem altogether unneceffary to infert the common Definitions and Problems ; yet, in order to refrefh the reader’s memory, when other books are not at hand, it was thought not improper to lay down fome few of the moft popular Problems ; and fuch | are thofe that follow., | ] PROB. ‘ Pen Bn Upon a given right line, to eet? another right line, which feall be perpendicular to the right line given, MTHE right line given is AB (Fig. 1.) upon ™ which, from the point E it is required to erect _ the Perpendicular EH. _ Opening your Compafies at pleafure to any cons ‘venient diftance, place one foot in the afligned point EB, and with the other make the marks C and D, equi-diftant on’ each fide the given point E, . Then opening your Compafies again to any other convenient diftance, wider than the former, place | one foot in C, and with the other defcribe the Arch GG; alfo (the Compaffes remaining at the fame di- ftance) place one Foot in the point D, and with the - other defcribe the Arch FF: Then from the point H, where thefe two Arches interfect or cut each o- ther, draw the right line HE, and it will bea Per- pendicular to the given ,right line AB; which was the thing required ‘to be done. : po GA oni! otro: P BiG B,, Tt. - ie To erect a Perpendicular upon the End of a right Line | “| given. alti . LE T. AB (Fig.2.) be a right Line = from the End. thereof, at B,: let ite to erect the Perpendicular BF. Firft, Your compafies being opened at - venient Diftance, place one foot in B, a1 other make the mark C ; the Compafs poi in C, with the other foot make the mark | - given line AB; lay a Ruler fro draw the line DE, making CE equalt from B, through E, draw the line B be the Perpendicular required, B2 SO ee ne ne ne on ne nee ee ee eS : | wey : Se PROB. III. Lo divide a given right Line into Two er Parts. LE T CB ( Fig. 3.) be a right the given, to be divided into two equal Parts. | From the extremes B and C, with ‘an SB Gance greater than half the given line, defcribe the arches above and below, cutting one another in the points _D and F: Draw DF, and it will divide AB into two equal parts in H, as required. . | , PROB Iv. Fo let fall a Perpendicular from any Point aff Fond, ee upon a right line given. rs T the point given (Fig. 4.) be C; from which point it is required to draw a right line, which fh] be : perpendicular to the given right line AB. | “ft, From the given point C, tothe line AB, an occult line at pleafure, as CE, which divide ual parts in the point D: Then placing t of the compafies on the point D, with the DC, deferibe the Semicircle CFE, cutting © line AB in the point FY Lafily, From C, draw the right Line CF, andit fhall be PROB. (5) : P.R O-B.. ¥. To makean Angle equal to om Angle given. TET the Angle given be ACB (Fig. 5.) and let it be required to make another Angle equal thereunto. Firft, Draw the line EF at pleafure ; then on the angular point C, as a center, with any conve-. nient diftance defcribe the arc AB, between the legs of the angle given; alfo upon the point F, with the fame diftance defcribe the are DE: Then take with your compaffes the diftance AB, and fet. the fame diftance from Eto D. Laftly, Draw the line FD, fo fhall the angle DFE be equal to the given angle ACB. | PROB. VI. i Aba given Diftance, to draw a right Line parallel to he a right Line given. ss TE T the line given be AB, (Fig. 6.) unto which — it is required to draw another right line parallel, - at the diftance MN, | Firft, Open your compafies to the diftance MN, then placing one foot in A, with the other defcribe. the arc C; alfo place one foot in B, and with the other defcribe the arc D. Lajfly, Draw the line CD, fo that it may only touch the arcs C and D ; _ fo fhall the line CD be parallel to the line AB, and at the diftance MN, as was required. | (6) PROBS VIB ) ‘A right line being given, to draw another right line parallel thereunto, which fhall alfo pafs through a point affigned, | Tt AB (Fig.7.) be a line given, and let it be required to draw another line parallel thereunto which fhall pafs through the given point C. ¥ _Firft; Take with your compaffes the diftanc from A to C, and placing: one foot thereof in B, with the other defcribe the Arc DE; then take in your compaffes the diftance AB, and placing one foot in the point C, with the other defcribe the Arc | FH, croffing the former Arc DE in the point H. Lofily, Draw the line CH, and it fhall be parallel ~ to AB. Thefe two laff Prostems may be more eafily per- formed by a parallel Ruler. : PUR O88 VIE: To divide a given right line into any number of equal parts. L= T AB (fig. 8.) be a right line given, and let it be required to divide the fame into five equal . arts. | if Firft, From the end A of the given line, draw the line AC, making any angle; then from the other end B of the given line, draw the line BD parallel to AC, (or make the angle ABD equal to the angle CAB) then upon the lines AC and BD, fet off any four equal parts (which is one lefs than the number of parts into which the line is to be di- vided) on each line, as1, 2, 3,4 then draw lines from 1 to 4, from 2 to 3, from 3 to 2, and from 4 - ta1, which lines, croffing the given line AB, fhall divide it into five equal parts, as was required. PROB, (7) P R..O Bai FX. Any three right lines being given, provided the two foorteft taken together be longer than the third, to make age @ Triangle. peri it i required to make a Triangle of the three lines C, B, and A, (Fig.g.) the two fhorteft whereof, wiz, C and B taken together, are longer than the third line A. Firft, Draw the line DE equal to the given line B, then take with your compafies the line A, and fetting one foot in "E, with the other defcribe the Arch HG; alfo take the given line C in your compafies, and placing one foot in D, with the other defcribe the Arch KF, cutting the former Arch HG in the point O: Lajily, If from the point O, you draw the lines OE and OD, there will be formed the Triangle ODE, whofe fides fhall be e- qual to the three given fiaes Ay B,C; In like manner, a Triangle /mm may be made equal to another given Triangle LMN. See Fig. 10. Alfo any rectilineal figure abcdefg, is made equal to any other rectilineal Figure ABCDEFG, by mak- ing the Triangles adg, bef, bfe, bce, ced, refpectively equal to theT riangles ABG, BGF, BFE, BCE, CED, See fig. 11. B 4 PROB, Ce) P-RO-B. ae ‘To reduce any irregular Figure into aT. rriangla, By he Problem the content of any pees piece of land may be caft up much fooner and more accurately than by the common method of dividing it palo “he ra- pezia and T riangles. | oF HE practice hereof bi via on sat re, Prop. of the 1{t Book of Euchd, where it is de- monftrated, that Triangles ftanding on the fame bafe, and being between the fame parallels are peu ene to the other, | ny | EXAMPLE. I. Let itbe required to reduce‘the Trapezium ABCD, Fig. 12. into-a Triangle, ngviie its Vertex at Angle A, Produce the bafe BC, and draw the diagonal AG thro’ D craw DE parallet'to AC, tllit meet BC in E, join AK and ABE will be the Triangle required. © fig. 13. thews how in- like manner. to reduce a Trapezium having a re- entian angle, EXAMPLE. Hf: Let it be required’ to reduce the Trapezium. ABCD, Fig. 14. to a Triangle whofe vertex fhall be at the point E in one of the fides AD.’ Join BE and CE, draw AF parallel to BE, and DG paralicl to CE, till they meet the bafe BC pro- duced in F and G, draw the lines EF ‘and EG, and the triangle FEG will be equal to the Trapezium given, -.* This Problem and itg Examples, are a Part of Mr. : Warner’ s Appindix to the laft Imprefiion of this Work. E X- ~ Pe wee EX AMP I.E. -Il ~ Let it be required to reduce the Pentagon ABCDE, | fig. 15. to a Triangle, having its vertex at the © Angle A. * ~ Produce the bafe CD both ways, and draw the . _ Diagonals AC, AD: Through B draw BF parallel to AC to cut CD in F, and through E draw EG pa- rallel to AD to cut CD in G, join AF and AG, and AFG will be the Triangle fought. " EXAMPLE IV. Let it be required to make a Triangle equal to the irregular Hexagon ABCDEF, and let the fide AB be one fide of the triangle Fig. 16. _ Produce tie fide DE, join AF, and parallel thereto thro’ F draw FH to mect DE in H ; join BD, and parallel thereto draw CG to meet DE in G; by B and G draw outa right Line ; join AG, and parallel thereto thro’ H draw HI tomeet BG produced in I, draw Al, and ABI will be the triangle required. | cig he 9 4 Oe ag Wg a EA To reduce any right-lined Figure given into a Triangle ; as fuppofe the. feven-fided Figure ABCDENVG, Fig, 17. Firft draw BD, and its parallel CK ; then if BK be drawn, it will cut off from the Figure the triangle DKS, and will take in the triangle BCS equal thereto, and the fide BK will fupply the ufe of the two fides BCand CD. Alfo, draw GE, and its parallel FL ; then if GL be drawn, it will cut off from the figure the triangle LRE, and take in the triangle GRE equal thereto, and the Side GL will fupply the ufe of the other two fides GF and FE, and the whole Plot ABCDEFG confifting of feven fides, is re- 2 duced on on oe oe ee yy yey rt ae a ce a a a ae ot ( TO duced to the five-fided figure ABKLG, yet aan Tome taining the fame quantity. Now to reduce this plot’ into a triangle, work in all refpects as in the Third Example, Firft, produce the Bafe both ways, then draw the lines AK and AL ; and parallel to them the lines BH and GM, cutting DE extended inH and M. Laftly, draw the lines AH, AM, and - they will conftitute the triangle AHM equal to the right-lined figure given, In like manner may any other irregular figure of ever fo many fides be reduced toa triangle, and that very readily by ufing a parallel Ruler, whereby we avoid drawing the unneceffary lines, only marking their interfections on the bafe. Thus in Fig.18. lay the edge of a parallel Ruler to the points B and D, then open the Ruler till the fame edge cuts the point C, and mark where it interfects the bafe DE at k ; lay the Ruler again to the points k and A, transfer i it to B, and ail its interfection on the ne ath; then draw Ah, which will be one fide of the Triangle fought.. Again, laying the Ruler to E and G, tranf- fer it to F, and mark the interfection on the bafe at ], lay the Ruler to | and A, and mark where its pa- rallel edge by G interfects the bafe prolonged at m. Laftly, draw A m, and the Triangle A hm will be equal to the feven-fided figure as was required, a gh SECA, ae A VE © blir 8 , Of InstRUMENTS ued 17 Surveying Land: NSTRUMENTS ufed in Surveying are, ei- ther to meafure, or lay down the lengths of lines, or their pofitions. ‘ The moft proper inftruments for meafuring ‘ lengths, in Towns, Streets, or any other Buildings, | are 5 Foot and 10 Foot Rods, and a Chain of 50 Foot long ; for Fields and Woods, a Chain, which from its contriver is ufually called Gunter’s Chain, and is in length 66 Foot or 4 Poles, confifting of 100 Links, each containing 7 Inches and +o 5 and a Rod, called an Offset-Staff, whole length is equal to <1, part of the Chain, that is, 10 Links, or’ 6 Foot 7 Inches and 2,, tho’ fometimes this Rod is 15 Links in length, or 9 Foot 10 Inches and +>. The Wheel is ufed with moft advantage in mea- furing of Roads. The Inftruments ufed for taking the Pofitions of lines are of two kinds, With fome we take the Pofition of a line, by the Angle which that line makes with the Meridian, ufing a Box and Needle ; as with the Z. heodolite, the Semi-Circle, the Circumferentor, the Plain-Table, the Perambulator, the Perador, 8c. and this is ufually called the Bearing of the Line. With others we take the pofition by the angle that the line makes with any other given line in po- fition; as with the limb of the Tbeodolite, the ae o SS ee ae nears : : : re B= Re eS. ee ee oe ie a ome - a pe a noes = aera new eeoS— = <5 = cs - = = = Saree as < = ¢ is ie ae ols oe es = oT x z . Lr. o el lg l glel Paty yy gr Leet rt ~— Seite Stee oe swore rer rs ba — (12 ) of the Semicircle, the frame of the Plain-Table, the Bevel, the Chain, or Rods. All other inftruments either aed from thefe only in their names, or elfe are contained i in them. = But with fome of thefe inftruments, very conve-~ niently we take the pofition in both cafes, at one obfervation ; as with the Theodolite, the Os or i.e Plain Table, With fome of thefe inftruments we take the ans” gle itfelf, as with the Bevel, or with the Plain Table cover'd with a fheet of paper ; and with others, we exprefs the relative quantity of that angle by num- bers. So when we ufe the chain, we exprefs the angle by Sextants, Links, and tenth parts of a Link ; when we ufe Rods, we exprefs it by Sextants, and centefimal parts of a rod; and when we ufe other inftruments, we exprefs the angles by de-s erees and minutes, We may alfo obferve, that of Theodolites and Semi=. circles there are various kinds ; in fome the Box and Needle is fix’d to the Plate, in others to the Indexes © And the working with each of thefe varies according to the manner of their Numbering, As for Roads, the Wheel with its Indices, fhew-' ing the diftance, and its box and needle with fights ni {hewing its bearing or pofition in refpect of the Me-) ridian, is an inftrument fpeedy and fufficiently exact : provided we reject the breadth of the road, and’ only regard the bearing and lengthy © me Lali (32 ) Laftly, Inftruments for plotting, are a feale deci- mally divided the whole length, clofe to both the edges ; and at every tenth divifion numbered 0, 1, 25 3, 4, &c. denoting Chains ; the. Number- ing fo ordered that we may counc either from the Right to the Left, or from the Left to the Right ; and a Protraétor always to be divided, numbered, and fitced according to your inftrument, Thus, all Circumferentors (either abfolutely fuch, or only ufed as fuch, wz, when contained in the Theo- dolite, Semicircle, or Plain Table) \et the numbers in the Protraéor increafe contrary to thofe in the box; but when the box and needle takes the bearing, as the Peraéior or Perambulator doth, the nurnbers of the Protraéor mutt increafe as thofe in the box. ind for khblimbs of all 7. heodolites, Semicireles, and Pilin Toblés. “if ‘the. citcuit be made eet te contrary ‘the numbers on the limb, thenumbers of the Pro- traffor moft conveniently increafe the) Tne way with the numbers on the limb of the inftru- » ‘ment, and this fuppofing the eye in the center. SECT. ie uc i H Hi 4 la i tae | ae eee SHE SAN Gis EN” > To obferve the Pofition of a Line by any of the preceding Inftruments. ‘ I. By the Circumferentor. HE Box of the Circumferentor is divided into 360 degrees, and numbered in 4 quarters, from the North and South both to the Eaft and - Weft, by the figures 10, 20, 30, 40, 50, 60, 70, ._ x 80, 90; but thefe divifions are alfo numbered from the North towards the Eaft or Welt, ali round, till they end at the North again ; by the figures ro, 20, 30, 40, 50, 60, 70, 80, 90, 100, and fo onto 360. _ Of thefe two ways of numbering, the latter is pro-. perly the Circumferentor, and the former the tra-— verfing Quadrants or Quarters. | Now, if it be required to obferve the bearing of the line AB (#7g. 19.) the Inftrument ftanding at A; the Flower-de-luce in the Box being towards you, direct the Sights to B ; and the South end of the Needle will point at 207 Degrees in the Circum- ferentor, and at S. W. 27, in the traverfing Qua- drants, And if you were going round the Field, and fo next to obferve the bearing of the Line BC; at B turn the Index about, the Flower-de-luce being to- wards you, till thro’ the Sights you fee the hair cut “€: Then will the South end of the Needle point at Illy 311, in the Circumferentor, (which is the bearing al- ways counted from the North, and in thefe Examples from the North to the Eaftward) and at S:; E, 69 in the traverfing Quadrants, which is the bearing al- ways counted trom the North or South towards the Eaft or Weft. Here we may note, that the bear- ing taken with the Circum/ferentor may be any nume ber of degrees not exceeding 360, but that with the traverfing Quadrants never exceeds ninety de- grees. apt be When you fufpect the Needle does not play well ; direct the Index to your mark, and note, ina wafte ‘piece of paper, the degrees pointed at by the Needle ; then with a clean Knife, or a Key, or any other polifhed bit of Steel, which has touched a Loadftone, move the Needle, by applying it to the Box, and when it hath fettled again, examine what degree it then points at, your Index being ftill di- rected to the preceding mark ; and if the decrees -are the fame, they may be entered into the Field- Book ; but if not, the Cap and Pin mutt be cleanfed ‘with fome brown paper and a little Puttey or Whit- ing, and thereby freed of fuch duft or dampnefs as ‘hath gotten to it; if, after all, the Needle doth not play freely, fcrew in a new Pin, or ufe another Needle, or do both. Thefe Neceffaries every Sur- veyor ought to have in his pocket while he is in the Field. | If you fufpect an error in the bearing of any line already taken, arifing from the Needle’s being acted on by fome hidden Magnetic power, or from your own miftake in obferving the degrees pointed at; the doubt may be cleared, and the error cor- rected at the next ftation ; thus, Having come to B (fg. 19.) the Flower-de-luce being from you, look back to A, and then will the’ South end of the Needle point at 207 degrees in : : the ( 16 s the Céeuailedvur me at S. W. 27 degrées in: the traverfing quadrants; juft as it did at A. | Laftly, if you have no reafon to fufpect ‘hie Needle, and it is moft convenient to plot by it, the fpeedictt way is to place the inftrument only at every other Angle, and there to take the ae: of the two lines which form that angle. So, if you would obferve the bearings of the lines of Fig. 19. firft place the inflrument at B, and with the Flower-de-luce from you, direct the ‘fights back to A, fo the South end of the Needle will point at 207 degrees in the Circumferentor, and at S. W. 27 degrees in the traverfing quadrants, which is the bearing of AB; then with the Flower- de-luce next you, direct the fights to C, fo the ° South end of the Needle will point at 121 degrees in the Circumferentor, and at S, E. 69 degrees in the traverfing quadrants, which is the bearing of BC. Now place the Inftrument at D, the F losbiule luce being from you, direct the fights back to C, fo the South end of the Needle will point at 44 deg. 30 Min. in the Circumferentor, and atN. E. 44 deg. 30 Min, in the traverfing quadrants, which is the bearing of CD; and dire¢ting the fights to E, the Flower-de-luce being towards you, the South end of the Needle will point at 102 Degrees 15 Minutes in the Circumferentor, and at S. E. 47 Degrees 45 Minutes in the traverfing Quadrants. In like manner work at F, €e. always keeping: the Flower-de-luce from you when you look back- wards, and towards you when you look forwards; fo will the South end of the Needle point at . the Degrees of the Bearing in both Cafes, | To: Be pe a whofe ae is takers » te a © 4 Circumferentor. : iR ST, draw lines parallel to one another quite tl ro" the pon ag draught, at diftances not ex- pa tof tieioreisctor on A, the bint given reprefent- d ing the ftation A in the field, and, by help of divifions continued beyond the ends of the di- ster of the Protraéior, lay the diameter parallel to thofe north and fouth lines; and if the Pro- tractor be only a Semicircle, lay the beginning of the numbering northwards, when the degrees are fewer than 180, but Recarts when ‘more: The Protratior being thus placed, make a mark clofe ta the limb againft 207, the degrees of the bearing, and thro’ it draw the line AB; and fo will AB have a bearing like to that, which you obferved the line | ABto have inthe field. In like manner you may lay down the bearing of any other line, as BC; if you obferve to lay the beginning of the numbering northwards, when the degrees are lefs than 180, and fouthwards when more: Butif the Protraéor be a whole circle, there will be no ,occafion for turning the beginning of the numbers, which may always be _ northwards, And if you would lay down the bearing of any line AB, Fig. 19. from any affigned point A, with the traverfing quadrants ; after you have drawn north and fouth lines as before, the north being upwards, write eaft onthe right hand fide of the map, and weft on the left, Now lay the center wf the Protraéor and diameter as before fhewn ; fave that inftead of obferving the number of the degrees, you turn the limb ‘of the Protraffor catt- C ward, Il. To obferve with a Vheodolite, both by Be Linb, 3 4 “wards you when the fixed fi ights are directed, and oe ay 18 )- a ward, when the bearing is N. Re or S, E. and wel ae ward, when it is N. W. or S.-W § 3 (a The Protractor being thus placed, “aha. S.W. 3 27. make a mark, and thro’ it draw the line AB, — and {o will AB have a bearing like to that which ~ AB was obferved to havein the field. In like man- ner you may lay down the bearing of any ac a line. c. oy : ee ee een . nite oa and by the Box and Needle. BEFORE you engage in a furvey, you ought to confider the numbering of your inftrument ; thus, when the eye is conceived to be placed in the center, confider whether the numbers increafe from. the left to the right ; or from the right to the left; or, according to the farmer’s familiar phrafe, whether the numbers increafe with or againtt the fun’s motion, a And then obferve, that with a 7, beodolite, shot box is fixed to the plate, the circuit-is moft con- veniently made with the increafing of the numbers; and the fixed fights fhall always be direéted to. the next ftation, and the index to the laft. But when the box is fixed to the index, ’tis beft to go — round contrary to the order of the numbers; and ~ then the fixed fights are to be direéted to the laft ftation, and the index to the next, And if the beginning of the degrees are kept to- the Flower-de-luce towards you when the index is direcicd ; the degres cut by the end of the index which is next you, are thofe which meafure the an- gle ; and the degrees pointed at in the box. by the fouth end of the needle, give the bearing of the next length. And this bearing will be, in all re- fpects, the fame with that taken by the Circumferene tors ee, 7 eat de tg 5 | ; tor i shoved that the box be divided and ere : e that - of the Circumferentor, x This double obfervation is of great ute to the urve eyor ; for hereby he may either plot by the an- gle, or the bearing, or by both, as he fhall find ~ moft convenient ; and alfo, may prove his obfervae tion before he moves the inftrument. For, of the _ numbers expreffing the bearing of the lines form- ‘ing any angle, if the leffer be fubtracted from the greater, and the remainder be increafed by 180 de- E43 _ grees when lefs than 180, or, if greater than 180, _ is diminifhed by 180; the refult in either cafe will _ Sive the angle itfelf, or its fupplement to 360 de- ee erees: as When a Theedolite 1s aed with a box fixed to the plate, and the numbersin the box increafe the fame _ way with the numbers on the plate; or, ° which comes to the fame, with the box fixed to the index, and the numbers therein increafe the contrary way with the numbers on. the plate (moft Theodolites be- ing made one of thefe ways, or fhould be fo to be moft convenient) ; then a Protractor being numbered contrary to the numbers in the box, will be fitted to lay down the plan, either according tothe angles. taken by the limb, or by the bearing taken with the needle, or by both together, in order to prove the truth of éach other: And then alfo may the truth of the angle or bearing be proved, before the inftrument is moved from the ftation by either of the two following rules. If to the prefent bearing be added 180 ene? and from the fum you fubtraét the laft bearing then the remainder will be the prefent angle. And if to the prefent angle you add the laft bear | ing, and fromthe fum fabtrack 180; then will the remainder will be the prefent bearing. Bl ae a C2 But | (20) a But if the degrees to be fubtraéted are more than thofe from which they are to be fubtra&ted ; the lat- ter muft be increafed by 360, and then fubtract. — 4 And if the remainder be more than 360, then — abate 360, and the refult gives the degrees re- quired. ih eae So, with a Theodolite that hath the box fixed to — the index, and the eye being conceived inthe cen- — ter, the numbers on the plate increafe from the left _ to the right, but thofe in the box the contrary way, and fo moft proper'to work againft the fun: If you would take the bearings of the lines of Fig, 19. be- ginning from any affigned angle, fuppofe A; then — your inftrument being planted at A, direct theindex to the next ftation at B, and the fouth end of the needle will point at 207 degrees in the Circum- ferentor, And for the following angles and bearings, when the | B i ie Al Be ts [B inftrument is} D{ direét the fix’d JC planted at } E fightsta )Df¢ F E G F J. C+ 2; ; D and there {crew the inftrument faft; } E a then direct the index to nN : A ‘ o & $4. 00 and the end of the index next your | 113. 30 ~ eye will cut on the limb the J237- 45 ig PRM te rea, SPARS 49» 35 | angles ae es = meeps 102, 40 asin the Circumferentor, point at oo. es oh. ae 308. 30 And with a Theodolite, that hath the box feed to the index, and the numbers of the plate contrary to thofe of the box, while the eye is conceived placed _ in the center, increafe from the right to the left, and fo moft proper to work according to the fun’s _ motion ; if you would takethe angles and the bear- be: sl of the lines of Fig. 19. and begin from any __affigned angle, fuppofe A; then your inftrument being planted at A, direct the index to the next fta- tion G, and the fouth end of the needle will point at 231° 30 in the Circumferentor. And for all the following angles and bearings, when the ak AG A ; , 23 oe eae G inftrument is} E { direct the fix’d JF ; planted at ) D fights to E { é C D B Cr F : E and there fcrew the inftrument faft ; } D then direct the index to : A and the End of the index next the} 1°2- 40 eye will cut on the limb the an-2 49> 35 gle = 64 = = = ~ = =a a 2.37- 4S a = is 4 Il3. 30 Cz and Tag ee: ( 22) 3B 30 +, ‘ Pe Silo ae 450 30 eg and the fouth end of the needle, as in} the Circumferentor, will point to the a bearing - + - 2 See But with a Theodolite that hath the soak fixed to. ‘ the plate, and the numbers on the plate as well as | thofe in the box (the eye being placed in the center) ‘increafe from the right to the left; and therefore moft proper to work contrary to the fun’s motion ; if you would take the angles and the bearings of the lines of Fig. 19. and begin at an affigned angle A; then your inftrument being planted at A, di-— rect the fixed fights to B, and the fouth end of the. needle will point at 207° 00, as in the Circumferen- tor, and as in the firft example. And for all the’ following angles and bearings, when the inftru- B meky oo ©: C fdireé&t the — 2 ment is planted at fixed fights? F F to G G A Ax 3 aiee then {crew the inftrument faft, and direét the }C Index to = a e a Sil it | F = 84. 00 113. 30] fo will the end of the index next the} 237. 45 { eye cut on the limb the angle 49+ 35 } 102. 40 234, 00 Le} | : eae III. eas ae of the needle, 2 44. he Circumferentor, will point at.71°?: — i) queen 331. | | 25 4. - 308. -: the sp ae the numbers on the plate, as well as hofe n the box, the eye placed in the center, ncreafe from the left to the right, and therefore sf moft | proper to work according to the fun’s motion ; if you would take the angles and the bearings of | the lines Fig, 19. and begin at an affigned angle vat A, direct the fixed fights to G, and the fouth end ‘of the needle will point at 231° 30 as in the fe- cond example, And for all the following angles _and bearings, when Bf . : tay ee Suh er te: 4 yes’: the inftrument is planted at _direét the fixed fights to wWOUnZMA then fcrew the inftrument faft, and teas me the index to... - ie 2 : 2 _ —_ QuMAOarrway and fo will the end of the index next ) 49. 356 | the eye cut on the limb, the angle 237+ 45 os C4 and ( 24) | and the fouth end of the needle, as in\2 © the Circumferentor, will point at the bearings = - - - Ba both as in the fecond example. be With either of thefe four ‘a(traknaHes ‘the angles — and the bearings of the Lines are taken, at once fet- ting the index, as eafily and expeditioufly as the angle itfelf only ; which evidently appears from the four preceding examples. And. the truth of thefe © obfervations may be readily proved, by either of ae rules already laid down. For, the inftrument being planted at B in fe firft and third examples, if to 111°00' the bearing there taken, you add. 180° oo’ and from the fum > 291° O0', take the laft bearing 207° oo, there will remain 84° oo, which gives the angle taken at Bee exactly as there obferved ; and proves the angle and thefe two bearings to have been truly obferved. In like manner, the inftrument being planted at C, in the fame examples; if to the bearing there taken, 44° 30’, you add 180° oo’, and from the fum 224° 30, you fubtract 111° 00, the bearing taken at the Jaft ftation ; the remainder 113° 30! gives the angle at C exactly as it was there obferved ;, which proves that the angle, and alfo the laft and prefent bearings are truly obferved. Alfo the inftrument being planted at D ; if to the bearing. there taken 102°15,, youadd 180° oo’, and from. the fum 282° 15°, take 44° 30! the laft bear- ing; ‘the remainder 23%7° 45! gives the angle at D, | as there obferved; . But the inftrument being planted at BE, if to the © bearing there taken, 331° 50 you add 180° 00" and from the fum 511? sa! you fubtract 102° 15, - the ue. FES | bearing ; the remainder 409° 35’ leffen’d by pecaufe greater than 360, gives 49° 35’, the {, And fo of all the reft. | in like manner may the angles and bearings ompared in the fecond and fourth examples. | ir the angles and bearings may be compared by the fecond rule thus: The Inftrument being planted at B, if to 84° oo’, the prefent angle, youadd 207° 30", the laft bearing, and from the fum 291° 00’ you take 480° 00’, the remainder 111° Oo, gives the prefent bearing, as obferved. _ The angles and bearings being truly taken, it remains to fhew how ~ _ Lo plott, and therein to difcover and correé an error | before it is communicated to the following part of tbe eS ead) Havre provided yourfelf with a Protractor, whofe “ numbers increafe contrary to thofe in the box, draw acrofs your defigned draught parallel lines, as in plotting obfervations taken with the Circumfe- venior. , Then having chofe a convenient point to repre- fent the firft flation, as at A, from thence, working by the firft or third examples, lay down the bear- ing 207° 00’, and draw AB, as fhewn in plotting from the Circumferentor. On the point B lay the center of the Protractor, and its diameter on the line AB produced both ways, if neceffary, fo that the beginning of the degrees may be towards the laft ftation, if the angle be lefs than 180°, but the contrary way, if greater ; and clofe to the edge of the Protractor make a mark againft 84° oo’, the degrees of the angle B, and draw BC, ‘Turn the Protractor about on its center, till the diameter be parallel} to the meridians, the beginning of the de- grees being towards the north, when the abitads : 2 efs (au om lefs than 180° ; but contrarywife when more $ ah if the line BC ras the bearing 111° -oo' on the ed of the Protractor, that line is ‘truly laid down ; b not fo, ifit cutany where elfe, But working according to the fecond Bnd fourth examples, lay down the bearing 231° 30’, and draw AG: On the point G lay the center of the Protrac« tor, as before fhewn, its diameter coinciding, with the line AG, and mark off the angle G, 234°0, — draw GF: Turn the Protractor, as before: andtie we FG cut 285° 30’ on the Protracior’s edge, the line a is truly laid down. oe Inlike manner, may any other angle be eased om and if found erroneous, the error may be corrected, before it is communicated to the following yoke of ; the work. . And we may obferve, that, if the plot be laid down by the bearings of the lines, thofe bearings may be examined by meafuring the angles as foon as plotted. . Though this method fufficiently recommends — itfelf, both in refpect of difpatch as well as accuracy 5 _ I do not expect it will be practifed by any but the — unprejudiced. For he who hath furveyed much land with a Circumferentor alone, or with a Semicircle or Theodolite, without a needles or with any other inftrument, that doth not aftord a double obferva- tion; he I fay, hath not provided a check to his frailty, and will fcarce forfake his old way, becaufe’ he will not accufe himfelf. There are two other ways to ufe thefe Theodolites, each equally exact with the former, but not fo ex- peditious. One way is to take the bearing with the traverfing quadrants ; the other is to take the bear- ing with “the degrees on the limb, But the angle i 1S always taken as above. If you would ufe the traverfing quadrants, thier the obferving, the plotting, and the proof in plot anes Es (67) ting, are all as eafily, fpeedily, and exactly done as by the | irft method ; but the proof of the obferva- im ner, is neither fo eafily performed, nor fo eafily reduced to one fingle rule. But the perfon who is lve to plot by the traverfing quadrants, had » 9 ft take the obfervation both by the Quadrants and Be Pioting by the eine eae __- Laftly, Vf you would take the direction or bearing * Be the divifions on the limb with a Theodolite, whole _ Box is fixed to the plate; then (having taken the angle as before fhewn) turn the inftrument about till the north end of the needle point .at 360 degrees in the box, and fcrew it faft ; direct the teed to the next ftation, and the end next you will give on the limb the direétion in sisal and minutes, as in the _ fermer examples. But with a Theodolite, whofe box is fixed to the index, if you would take the direction by the di- _ vifions on the limb ; then (after the angle is taken, as before fhewn) direét the fixed fights to the next ftation, fcrew the inftrument faft, and turn the in- - dex about till the north end of the needle point at 360 degrees in the box; and then will the end of the index neareft to the fouth end of the needle cut on the limb the direction in degrees and minutes. ~ But .the Protractor to lay this bearing down, mutt) be numbred contrary to the limb on the inftru- TMB 024° ae field, though equally true with the. hw The great advantage ufually propofed by this laft . method, is, that the degrees on the limb are larger and more diftinétly cut, and confequently more nearly eftimated than thofe in the box. But con- fider that you can no better bring the needle to polit at any one degree, than you can eftimate its pofition in pany other degree ; and that fince we ufe the piss a + nat nom —_ —o a ie, ital ie Ff yt ( 28 ) | all the objections made in one method are incident to the other ; and then you may eafily conclude, that the advaniage 1s only imaginary. | Befides, here we are obliged to take two obferva- tions, either of which take up as much time as the : obfervation ufed in the former method ; seiidh rene | . ders it not fo fit for a practitioner. 3 ‘a Of the ufe of thefe Theodolites, I have one thing more to advertife, viz. To meafure and caft up the. content of one ‘large fingle Wood or Common, where there are fome fcores of angles to be takens the fafeft way is to caft, without plotting, by help of the needle. And in this cafe I would take the direCtions both with the Civcumferentor and the tra- verfing Quadrants ; andin the field prove the direc- tions taken with the Circumferentor by the angles taken by the limb ; and then, {till in the field, prove both lengths and directions, in calculating a traverfe, by help of a Traverfe Table ; and laftly, from this ~ traverfe (at leifure) deduce the true content. . But the Traverfe Tables that are naw extant, are’ but fpecimens of thofe which are fit for ufe; inftru- ments are not fufficiently exact, and trigonometrical operations too laborious, and therefore this way of | computation muft be deferred, till fome perfon who hath leifture and patience to ferve the world, imcalculat- ing fuch a table, is refolved to do it *. Of any one of the four 7 beodolites, which have the numbers in the box contrary to thofe Theedolites: before defcribed, one or more inconvenience will al- ways arife, ufe which of the three forementioned methods you pleafe. It is true, the angle taken by the limb is per-: formed as fhewn in the preceding rules but fince: * Here the author promifes if he can procure fuch a table, as he hoped to do, to publifh it with its ufes in Prae- tical Surveying and Navigation: But he being long fince dead, that defign has dropped. 1} : it ee ees not fafe to work by the limb only, if you ufe the ircumferentor, as fhewn in the firft rule, you mutt ner fubtract the direction from 360 degrees, and the remainder inftead. of the direction pointed by the needle ; or elfe ufe two Protractors, which be troublefome, and alfo apt to caufe miftakes ufing the one for the other. Dead: eee" x ‘IF youufe the ¢raverfing Quadrants only, then in- _ deed the ufe is in all refpects the fame with the pre- _ ceding ones; but thefe, as I have already thewn, are not fo expeditious as, nor more exact than, the method firft laid down. | _ If you will take the direétion by the limb, and ftill make one Protractor plot both obfervations, you muft direct your inftrument twice, whereas by the firft method laid down, it might be done at ance. : | Lafily, Of Theodolites thofe are beft which have telefcopes with plain fights on them, and fo con- trived that the furveyor may at any time adjuft any {mall accident, without coming to a workman; and that both of them may be elevated or deprefied at leaft ten degrees ; one of thefe telefcopes inftead of the fixed fights, the other inftead of the moveable ones, and as long a needle as will play well, with other the like conveniences, fufficiently known to a Akilful inftrument-maker. HI. ( 30) Ill. To obferve with a Sevnivircll ‘that bath a Bas and Needle, ee, i Semicircle is juft half the TZ, Geodtlite a ibannicl ing of juft as many varieties ; it is numbred on the 4 limb to 180 degrees, and in an arch concentric to this is denominated by the numbers 190, 200, 2403. &c. to 360 ftanding under the former numbers 10, 20, 80; Coro 1s ule, in all refpeéts (both to the plate and box) is the fame with the Theodolite ; fave in this, that when the end of the index next the eye, _ q falls off the plate, the degrees cut on the limb are to be taken from the further part of the index reckoned among the divifions of the inner circle, and will be oe always more than 180 degrees. There are other ways of numbering and dividing (and perhaps without a box and needle) ufed in thefe inftruments ; but they are not worth notice. / IV. Of the Peratior. TH FE, Peractor is the fame with part of that 7 heo- dolite, whofe box is fixed to the plate; and the directions given for the Theodolite in page 27, will ferve for this, ere “a SHE E Bivihions’« on ah limb bP the Plain Table, with its box and needle, being like thofe of the eodolite, or modern Circumferentor ; ; if the 360 de- rees on the limb be upwards, and the box and needle ferewed to the fide of the table; it performs, in all refpeéts, the ufe of the Theodolite, whofe box is fixed to the plate, For lay the edge of the index on the divifion numbered 360, and to that numbered _ 180; and turn the whole inftrument about, till [. “through the’ fights you fee the next ftation (the 360 being: “towards: you, as fhewn with the Tbeodolite) and ‘there ferew it faft; ‘then turn the index about upon the center, till you fee the laft ftation, and fo ewill the end of theindex next you cut the degrees of _ ‘the angle, and the fouth end of the needle will give - ee ioe direétion or bearing. ~ But if the box be fcréwed to the nde, it in like manner becomes a Theodolite, with a box fixed to the index. _ If the box and needle be {crewed to the ftaff, it is a Circumferentor, _ If the box be fcrewed to the table, and that fide of the frame be upwards, which is divided into four nineties, it is the Perambulator. If that fide of the frame is upwards, which hath only the 180 degrees of the femicircle numbered on it, then it is a femicircle, either with the box to the plate or not, according as the box is fixed to the table or to the index. And what hath been already faid of thefe inftru- Mments may ferve for directions, to ufe the plain table thefe feveral ways, and need not be again repeated here, | And (32) properly be called Panorganon, or the tinlyetlall ins: - {trument, in refpect of land furveying, Poa There are two fmall holes towards the middle one . the board, which ferve as centres to the divifions on 4 the limb ; the one for thofe when the table is ufed as a femicircle, the other for the degrees numbered as in a Theodolite: In thefe holes the protracting pin is to be fet while the floped edge of the index flides againft it, and cuts the divifions on the frame. Now if thefe holes were conical, and were the con=- _ tinuations of a conical hole in the index, {fo that the index could be fixed to them by a conical pin paffing thro? its hole, and the central one, into which the pin icrewed, the fiducial or floped edge of the index being made to correfpond with the center of the pin ; alfo if the divifions on the frame be cut as accurately as on the limb of a Zheodolite ; and the wood would neither fhrink nor {well any more than brafs; and a telefcope mounted on the fights ; and the back fide of the index brought alfo to a fiducial edge; then the plain table would be a very compleat ins ment. It remains to fhew, how to take angles when we ufe the plain table covered with a fheet of paper ; but this hath been fufficiently handled by Mr. Ley- bourn, and almoft all the common writers on Sur- veying ; therefore I fhall content myfelf with laying down a method to correct an error committed be- | fore it is communicated to the following partsof the work, Though I do not any ways doubt but the reader may, by what follows, learn the ufe of this plain inftrument. Suppofe you were to draw the plan of the field ALMNQR: (fig. 20.) Draw on the table a line to reprefent AL in the field, and by the fcale lay cown on the plan the length AL was found to be in ‘the field, when you meafured it with a chain, Then ( ideale Then p inting the table at EB, lay the index on AL} and oe the whole inftrument about till you feea _ mark fet at A, then {crew it faft, and turn the in- dex : about on Las a centre, till through the fights you fee M, draw LM, and by the fale, give it on the table the fame length you found it to have in | dae, by meafuring with the chain, Yow in order to examine the length of LM; and fo its pofition in refpect of AL; “plant the inftru- jent at M, lay the index on LM, and by turning Po he inftrument, direct the fights to L, and dices {crew it faft ; chen direct the index répned about on M, towards A in the field, and if the edge does not cut the point A in the table, the line LM is falfe, either in pofition or length, and therefore muft be examined and corrected before you proceed. The line LM being truly laid down, plant the inftrument at M, lay the index on LM, and direct the fights to L, by turning round the table, and fcrew the inftrument faft : Now turn the index a- bout on M, till through the fights you fee the hair cut N, by the edge of the index draw a ftrait liney ‘and by your fcale, from M lay the length NM e- ~ qual to what you meafured it in the field. But to prove whether the line NM is truly laid _ down both in pofition and length ; having planted the inftrument at N, and direéted the index laid oa _ NM to M, and there fcrewed ‘the inftrument falt.; - from N direé&t the index to either of the marks L or _ Ain the field; and if the index then does not acs oniely cut L or A on the table, the line MN is _ falfe, and muft be corrected before you proceed. And in like manner through the whole furvey, you may proceed to lay down every line, and ex- amine it before you leave it, (provided that you leave all your marks ftanding at the ftations,) by ays the index on the latt line, and turning the inftrument about till thro’ the fights you fee the D hair | G4, i hair cut the laft mark ; and then fcrewing the ‘nick 4 ‘ment faft ; if you turn the index about on the point — reprefenting the ftation where the inftrument ftands, — till you fee any one of the marks paffed by, except — the laft of all; and if the edge of the index does not — cut on the table: the reprefentative of that point, the. i laft line is not truly laidddown. - But when frem any ftation, fuppofe N, you can- not fee any other mark but M, fet up fome mark Aya from whence you may fee fome of the preceding marks, fuppofe L, as well as M and N; and from — this point a examine the truth of the pofition of Ps . line MN. : Or thus; you may fet up a ia a, any where in — the field, from whence all, or feveral of the angles © may be feen ; then the inftrument being at A, and © the index on AL, fcrew the inftrument faft; and turn the index on A, till youfee a4, and draw Aa, The inftrument being at L, the index on LA, © and the index direéted to A; lec the inftrument be {crewed faft ; turn the index about on L, till thro’ the fights you fee a, draw by the edge of the index - La ; and fo will the point a be determined. a Then the inftrument being at M, the index on © LM, the fights directed to L, and the inftru- ment {crewed faft ; turn the index about on M, till thro’ the fights you fee the mark a in the field: Then if the edge of the index does not cut ain the _ table, the line ‘LM is falfe either in pofition or lencth. Py inililee manners eae being at N, the index om : NM, the fights directed to M, and the inftru- ment fcrewed faft ; turn the index about on N, and direct the fights to the mark a ; and if the edge of the index doth not cut a, on the table, then MN is falfe either in pofition or length. ha Laftly, inftead of a mark fet up as 4, you may afe any remarkable tree, fteeple, &¢. not at too | ( it erea j | (35) ‘great a diftance from you, whether it be in the land | “you are then furveying, or not. And when the mark you have laft ufed is at too Fe fo diftance from you, or lies almoft in the fame trait line with that which you are about to lay down ; en ule fome other mark in its ftead. evi Of working with ihe CHAIN, G Fe ST, provide a ftaff juft 6 foot 7 hes and = two tenths long, which divide into 10 equal - parts ; and fo will the whole be the length of 10 links, and each part the length of one, and 10 times the length of this ftaf, the length “of the whole ~ chain. | ~ With this ftaff examine the length of the chain, and alfo of every 10 links; ftretching it on level ground, to fuch a degree as you defign to ftretch it, in the field work. Before you meafure with it, provide 1o arrowsor =“ final fticks, each about two foot long» and of fuch _ thicknefs, that a man may conveniently grafp 10 of them in one hand; alfo two ftrait ftaves about 5 foot _ long each: The arrows may be made of Ground > Af, a.tough wood and not aptto break ; let them be thod with fharp-pointed iron ferrils ar one end, and have pieces of red rag tied at the other ead, whereby they will be very readily diftinguifhed and _ difcovered when fet down in long grafs or corn. When you are about to meafure with the chain, Jet him that leads it take the 10 arrows and one of the ftaves ; and he that follows it the other ftaff. Then the follower ftanding at the ftation, let him by motions with his hand to the right or to the left, _ as they have before fettled it, direct the leader to a Ee his 5 foot ftaff at the chain’s end in the fame ight line with the ‘lations ; and then let the leader D 2 take ( 36 Ye : ¥ take up the ftaff, and in its place flicking down one — of the arrows, go on. . Now the follower being come to the arrow, take it up, fets his {taff in the hole, and directs the leader to place his flaff as before. And then let the leader, ftanding at his fae look back towards the laft ftation, and he will fee ‘ the ftaves and the {tation inone right line, if they _ have directed right. But if they are not inone right line, the leader muft direct the follower to place his: : ftaff at the chain’s end, in the fame right line with the ftation, and the teaser s ftaff, And fo, let each direct the other, till ee two flaves and the two ftations are in one right line ; and then muft the leader put down an arrow inthe ~ place of his ftaff, and go on: And the follower take — up his ftaff and the arrow where he laft ftood, and go after him. 7 And let them thus proceed till they have meafured to the ftation, or till the leader is nearer the ftation than one chain’s length ; and then will the number of the whole chains meafured, be exprefied by the — number of the arrows pricked down by the leader, and taken up by the follower, which fuppofe 8. ¥ Now let the leader go on to the ftation, and there hold the end of the chain, and let the follower ftretch the chain as ufual, and then fee how many links are — contained between the laft arrow and the ftation ; which may be readily counted by help of different. bits of brafs, or curtain rings, or other marks fixed at the end of every tenth link, which links fuppofe to be 47. Then enter in your field-book the chains and — finks without any diftin€tion between them, and — they will be 847 ; which imply either 847 links, or -8 chains 47 links. But here we are to obferve that the links muft BD ways pofiefs two places 5 as 8 chains and 4 links muft up €3>.) | mutt be written ie ; that is 8 chains and 4. links, 804 links and 8 chains without any links, muft be * written 800, implying 8 chains, or 800 links, Te is neceflary that the furveyor fhould enquire of — his affiftants at the end of every meafured length, how many arrows each hath; and if the fum of the - arrows are not ten, it is evident they have dropt or deft behind, thofe that are wanting; and confe- quently the laft length meafured is doubtful, and muft be re-meafured before you proceed, _ When you are come to the ftation, if it be con- _ venient to continue the length, let the “follower ftand at the laft arrow, and let the leader go on with the ‘chain, and fo place his ftaff, that it and the two fta- tions are in one right line ; then in the place of the fiaff put down an arrow, and goon; always direét- ing himfelf to place his flaff, and confequently his arrow, by the two ftations, When you have continued your length, till you have nearly loft fight of the fartheft ftation, fet up another ftation-ftaff in the place of the laft arrow, © and continue the length by the two neareft ftations. But withal take this caution, that it is not fafe to continue lengths very long, when the flations are near one another, When your length is very great, having mea-~ fured ten chains, let the leader go on and fet his ‘ftaff down at the eleventh ; ; now let the follower put his ftaff in the place of the leader’s, and give the Jeader nine arrows, and then goon. But obferve “to enter in the field-book thefe ten chains, and never truft to your memory. And if the length confifts of ten chains more, work as before, and en- ter 20 chains, and fo on. For a fhife, the furveyor may perform many works with the chain ; but this at beft is both Jabo- rious and tedious, the only inftruments for furveying ~ all manner of lands both great and {mall in all cafes, D.3 being ( 38 ) om being the Theodolites before mentioned; yet left there fhould fometimes be an abfolute neceflity for taking the pofition of a line by the chain when other inftru- — ments are wanting, we have here added the method ~ of taking an angle therewith. . In ordex to do this, provide three round fticks, — very ftrait, and about four or five foot long. And if you were to take any angle as DBC (Fig. 21.) fir place one ftick upright in B, and there hold one end — of the chain, and let your affiftant carry the other — end and another ftick towards C, and direct him to — move fideways, till the ftick held upright at E, be © exactly in the right line BC, at the chain’s end, — where let him leave it. Then let him take the end of the chain and move — towards D, and, as before, direét him to plant the ~ third {tick at the chain’s end upright in the line BD at Pe. | : Then meafure the diftance EF in links and deci- — mal parts of a link, if lefs than one chain, and enter them in the field-book : So if the diflance EF were — 94 links and 7 tenths of alink, they might be enter’d — thus, o° 947s. denoting o Sextants, 947 Parts ; the fextant ftanding for the chord of fixty degrees, In this work great care ought to be taken, that — the fticks be as ftrait as a workman can fhoot them — with a long plane ; and that they are planted either exactly perpendicular, or at Jeaft fo that the fticks planted at B and E, and the mark C may be exaétly in the fame plane, and alfo the fticks B and Fy, and the mark Din another plane. | But becaufe it is very difficult to ereét a ftick ex- actly perpendicular, it will be cafier to perform the — Jatter thus; plant the ftick as nearly perpendicular as you can; then move yourfelf backwards towards G, the farther the better, till your eye, the ftick at B, and the mark at C, are all in one ftrait line, — there ftand and direct your affiftant to plant his ftick, fo salt ey oe oat veo ) fe that the ftick at B exaétly cover it from the top ~to the bottom. But if it fo happen, that you cannot move back-. wards at all towards G; then having planted the flick at B, as upright as you can, let your fecond . _affiftant move forwards towards C, and let him there direct your firft afliftant to plant the ftick at 1a fe _ that it exactly cover the ftick at B, while you direét _ him to place it in a right line with the ftick B and the ~ mark at C; and the like caution mult be ufed in planting the flick F. Neverthelefs it will often hap- pen fo that the mark at D may be a little fhifted, and in this cafe, time and trouble may be a little leffened ; for having planted the ftick at F nearly in a true pofition, move forwards towardsD, and - direct your affiftant to incline the ftick at F, fo that it exaétly cover the ftick at ‘ then returning to By. direct your affiftant at D to place the mark in a right line with the fticks Band F. ‘But, fecendly, if the angle DBC is fo great that the line EF be longer than-the chain (as in Fig.-22.) lay out a fextant ; thus while the chain was Jaid from Bto E, fet down an arrow at H 50 links; then let your affittants hold the chain’s ends at H and B, while you with the middle in your hand, move to- wards I and lay both halves ferait ; fet down an ar- row at I, which conftitutes the equilateral triangle HBI; and thereby gives the angle HBI a fex- tant. Now the chain’s end {till held at B, ftretch it through the point [| to K, whiere alfo fet down an. atrow ; then meafure KF in links and decimal parts of links, which fuppofe to be 76 links and 4 tenths; and then fhall be entered. in the field-book 2° 764, implying one fextant and 764 parts. Tn like manner, if the angle were more than two fextants (as in Fig.23); then n having laid off the fex- tant FBI, let your affiftants hold the ends of the chain at B and I, while you with the middle of the D 4 chain . ° ( 40 ) chain in your hand fet down an arrow at L, confti- tuting the fextant IBL ; and then as before, the chain being ftill held at B, Jay it through L, and at ~ the other end K, fet down an arrow; then mea- ~ fure FK, which fuppofe to be 43 links and 5 tenths, and enter in the field-book 2°435, that is, 2 fex- ~~ tants and 435 parts. If you would continue a ftrait line, fignify it by entering in the book 3000 3; that is, 3 fextants. If an angle be external, and fo contain more than three fextants (as in Fig, 24); let one affiftant hold one end of the chain at B, and let the other affiftant ftand with the other end of the chain at E, and there hold a ftick, fo that E, B and C, are in the fame © plane as before fhewn ; and let him alfo plant a ftick atF’, fo that the fticks B and F, and the mark Dbe alfo in the fame plane. Then meafure the angle EBF as before, and to it add three fextants, and fo will the fum be the meafure of the external angle CBD. So if the angle GBD be o8 947, then will the external angle CBD be 3° 947. But if the angle GBD be 1° 764, then the external angele CBD will 4°764, And ifthe angle GBD be 2° 435, then the external angle CBD will be 5° 485. Now to plot any of thefe angles thus taken (fup- pofe that in Fg. 21); chufe fome line divided into 4000 equal parts, and with this line as a radius from the center B defcribe an arch ER, and lay thereon from E to F 947 equal parts and draw BD, And if youwould plot the angle taken in Fig, 22 3 from B with the length of the divided line, defcribe an arch EF’, and lay thereon the length of the divided line from EF, to K, and afterwards 764 parts from K to F, draw the line BFD, and you will conftruct the angle required. | . Again, i 7 (41) Again, if you would plot the angle of Fig. 23; then as before, with the length of the divided line, from B defcribe the arch EF, and thereon lay EP, _ PK, each equal’ to the radius ; and afterwards lay 435 equal parts from K to F, draw BF’; and you _have the angle required, _ And if you would protract an angle greater than - three fextants (as the external angle CBD in Fig. 24); _ firft continue the line CB, then from the angle fub- tract three fextants and make the angle GBD equal to the remainder. Angles about gardens or buildings may be taken with rods of 5 and zo foot, and laid down in all re- fpects as with the chain, but are no ways fitting for large plans. _ | Ifthe furveyor has only a chain, and having” drawn his plan, would draw thereon a meridian line ; he may do it thus; exaétly at twelve aclock, mark the fhadow of fome upright object, as the corner of a houfe, or fome ftrait tree, or your ftaff fet up- right ; then plot this line on your plan, and it is a meridian line, : Or thus; in a night when the Pole-fiar is to be feen, place yourfelf fo, that your eye, the Pole-ftar, and fome upright object, as the corner of a houfe, or the fide of a ftrait tree, be in one {ftrait line; then plot the line from your feet to the upright object, and it will be a meridian line, Indeed the Pole-/far moves round the real pole ; but at fo fmall a diftance from it, that in this cafe the variation may be rejected. How- ~ (42). However, you may obferve that the Pole-ftar is ¢ March and September at 12,) | April and Offober at 2, full north about ! AZayand November at 4, | ‘the 20th day of | Fune and December at 6, | Fuly and Fanuary at 8, | L Augujft and February at1o J a clock either morning or evening ; always increafing ~ nearly 2 hours for every month. Therefore if the obfervation is made about thefe times, the variation will be very inconfiderable. Alfo obferve, that 5, 6, or 7 hours before or after thefe times, if the pointers are to the eaftward of the pole, then the variation of the ftar is about 3 degrees and a half weftward ; and is then the oreatett. But if to the weftward of the pole, the variation ~ is about 31 eaftward, and then at the greateft, Note, The pointers are the two hinder wheels of the conftellation called Charles’s Wain, which are gbferved to be always in a direct line with the Pole-fiar. Speer. x oa ¥ ae 5 \ \ A ie Se oe at To cat up the Contents of LAND, with the Method of reducing lrregular Curves ¢o Strait Lines, HE contents of any field may be readily caft up thus: Take each bafe and perpendicular of every triangle, and each diagonal of every Tra- pexium, in links, efteeming every chain 100 ; inevery Trapezium multiply the fum of the perpendiculars by the diagonal ; and in every fingle triangle, the bafe by the perpendicular; then add the feveral pro- ducts together: Put a point between the fourth and fifth places, and another between the fifth and fixth, reckoning from the right hand; then halve the figures to the left hand of the points, and fo will this half be acres; if an unit remain, that unit is an half acre or two roods; and if the figure between the points be five or more, take five from it and ac- count it another rood. Then, multiply the remain- ing figure o between the points, by 8, and-to the product add the tens to be carried from the fourth figure, and you have the perches. If any perfon is fo curious, as to efteem the decimal parts of the perches, they will be the product made by multi- ~ plying the figures to the right hand of the point by 8. So in figure 25 the operation will be thus. 313 ( 44 313=AC; 214=KL; FG=418_ 612=DE; 396=HI; ie Pa 925 610 2am 6200 725 = BF 500=FM as 4625 305000 1850 7 6475 670625 a! 305000 — 670625 | 376200 13]5|1825 AVRYT. Anfwer, 6:3:31 Here half of 12 gives 6 the acres, and one re- maining is 2 bras ee ; then the 5 between the points gives another rood ; and fo the whole is 6 acres and three roods ; and becaufe there is but one ten to be _ carried from the fourth place, and that after the 5 is taken out of the fifth, there remains nothing, there is but one perch, In like manner, if the whole fum of all the A. Rie 171415304 8.2.36 Products }11]9|2765 (the con-} 5.3. 34 be 10/5/4321 ( tent is )5.1.03 81413764 4.40.35 So if the fum of the products be 4117|6354, the content is 20. 3.. 2110832. But this method muft be only ufed when the figure is reduced to triangles and trapeziums, It may not be improper, to add in this place, the manner of cafting up fuch fields as confift of many {mal} ot - 4 » ee ea, TP eo ae pe = aa - fe x. 5 ae pes Ni a Re oF A a eV ae { “ af ERA Bie Rae “> Po aC pear Oe Aen i see ee ee a tinnrces P > o ~ a ae 2 A ei 7 < ss ‘ | — (45) {mall breaks in the hedges ; without reducing them to a multitude of triangles ; thus. Let Fig. 26, be fuch a field; produce NM, one of the longeft fides; then lay the edge of a ftrait : _ tuler from M, one of the angles at the end of NM, | to G the next angle but one ;_ holding the ruler thus faft, take with a pair of compafies the diftance from L to the edge of the ruler, and with this diftance let » one point of the compaffes move gently clofe to the ruler, while the other point traces out a line parallel to it, and croffles NM in Q. Now draw GQ, and it will reduce that fide of the figure, which was ‘bounded by the two lines ML LG, to another bounded by GQ, one fingle line only. In like manner QG being produced, and a ruler Jaid from G to BE, carry the diftance of F from the ruler parallel to it, till you crofsQGin K. Then lay a ruler from K to the next point D, and carry the diftance of E from the ruler parallel to it, till you crofs QGin H. Now lay a ruler from H to- the next point C, and carry the diftance of D, the ~Jaft point from it, parallel, till you crofs QG in I. Laftly, draw IC, and the fide GC which confifted of the four lines GF, FE, ED, DC, will be reduced to the fide IC, confifting of one line only. And in like manner we might proceed if the lines were never fo many. | - And thus laying a ruler from C to P, draw PO, and in likemanner AQ. So will the ten-fided figure be reduced to a four-fided one, and fo may be caft up by one multiplication only. The practice of this will be rendered vaftly eafy by help of a parallel ruler, | Provide a plate of thin brafs in form of an arch of a circle ; near whofe ends let there be drilled fmall holes, through which ftring it with a very fine hair or wire.. Being thus provided ; when a hedge at GC bends in and out in feveral places, and thofe 4 | bends SSS SS \ ( 46 ) : bends contain very fmall fpaces, lay the hair over it lengthwife, fo that the quantities thereby cut off from the figure may be equal to thofe added to it; and with your protracting pin, near the ends of the hair, make two marks, through which draw a {trait line ; and fo will this irregular fide be reduced to a reoular one. And here we may obferve that in very {mall bends, we judge better by the eye than we can by the compafies of the equality of the parts taken in and left out. But, if hedges confift of large curvatures, chufe out fuch points, and fo many of them, that right lines drawn from: point to point, may vary the quantity by fuch parts only as may be rejected. And herein your hair will be a ready affift- ance, \ SSPE RR bee Lot o4 S 20S SEO ESO Le LOBOS ORIGOLO LUST OOPS TOG OL ORS J oe Cubeeys Of the Laying out, or Dividing of LAND. (4 7 HEN any number of acres, roods and ¥ ¥ perches are to be laid out, or meafured off from another field, it is convenient to reduce them to iquare links, which may be done thus: I 40 If the roods are? 2$ add 2 80% to the perches, 3 120 and to the fum annex 4 cyphers. Divide this laft by 16, or by 4 and 4, and write the quotient figures, if they confift of 5 places, after the acres, But when the number of quotient figures are but S ‘ ; write a oe ners pater the acres, and then the quotient hgures ; ana fo will you have the fquare links required. Ex, Fr. \ F i. - a a ‘ a? ite A, | == A alee “A PROP. Ex.I. Reduce 7 2 24 to _[quare links. bay to 24. perches, | mere. Add 80, becaufe 2 roods E ae '16)1040000(65000 _ ie | 80000 © : Anfwer 76 thes me | AR, oP. Fr? Ex. JI. Reduce 7 Oo 11 ¢to fquare links. b3 | Me ies perches ¥ fda o becaufe o roods, 4)110000 i 4) )_ 27500 Ghioliine Base 6875 bas four places: 3 Anfwer 706875. A REOR. Ex. III, Reduce 7 0 on to fquare links. to o1 perches, Add o becaufe o roods, 16)10000(625 three places 40 : 80 _ Anfwer 700625. we A K,: PB, _Ex. IV. sib ine 13 3 37 40 square links. "perches, Ma 120 = becaufe 3 roods, 4.)1570000 4)392500 uotient 98125 bas 5 places. = Anfwer 1398125 /quare links, In (as : Tn the ope out of lands, there ate three Be 3, or Problems, which arife in practice, For, citer the partition line is required to be pa- rallel to fome other line affigned, or is to pafs thro’ _ fome point affigned in the fence, or to pafs through fome point afiened within the land. In the folution of each of thefe cafes, I chufe an- arithmetical approximation rather than a geometrical conftruction ; for reafons fufficiently known to thofe | who have practifed. Note, When a quantity of land is to be laid out, or taken off from a field ; itis neceffary to have an exact plan of the place, or field; and this is aps 3 one in the following problems. . Oo v6 ms % Rae ROR ao 4% 5e0% PROB. =_ = t it be required to cut off towards AB, 8 Acres; 3 Roods, 18 Perches, by a line drawn parallel to _* near the place where tis imagined the partition Tine fhould be; and then caft up the content of the figure CDHG, which fuppofe to be 772575 fquare Tinks, which is. lefs than 84: 38 18P-, or 886250 -fquare links, by 113675 fquare links ; which fhews, that the partition line fhould be more towards K, _ Now divide the excefs 113675, by 965, the Tength of CD in links, and at the diftance of 118 links, the quotient, draw EF parallel toCD, and is will be fufficiently near the partition line required. — But if by curiofity you are led to correct the va- ration; you may conceive CD to be a line given in pofition, and 113675 fquare links, to be the quan- tity to be cut off, and EF the line drawn by guefs. But if the line CD had cut off the quantity CDHG greater than that required; then the partition line had been more towards GH, whofe diftance fromi CD would be found as before, by dividing the dif= _ ference by the length of CD. 7 ea PROB, From the Field LMPQRSTW, Fig. 28. zi 4 To cut off 5% ih 35°: towards the corner Ly by. a ie ne . drawn from the point Vere ™“ Re ite given quantity 54: oR 3 SP. to ‘quare links, and they will be 521875. ae Then draw LV, forming the triangle VLW, which being caft up, amounts to 30800 fquare linkem which is too little. a To the next angle draw VM, ining sid tril angle VLLM, which being caft up will be “found to” amount to 294632 fquare links, which added to the triangle VLW, you have 328432 fquare links, the content of the Trapezium VWLM, which is fell t too little. i} To the next angle draw VP Saha 3 another nl 32843 the content of the BB ‘figure, gives | 732282 {quare links; which is more than the re- quired quantity, by 210407 {quare links ; therefore i the partition line muft pafs between P and M. Divide the excefs by 497, half the length of vO | the perpendicular in links, and lay 423 the none | from P to N, and fo fhall VN be the true line om Partition. . Seer oe an rae att Sara pee te Ae mae ae pee ae tee GE: ( Su) ca ra 'p ROB. Tih te, 3 By io) Seat this with one fie: : Confider ‘ieouck which two fides of the field the partition line will pafs. Reduce the figure to a Trapezium, full retaining thofe fides, as fhewn in page 45. Which | divide by a line through the affigned point A. bm But, becaufe this weed is ie eg and depends “on the concourfe of many lines ; and though we — fhould ufe numbers, we fhould fide mend the mat- ter, and indeed is often impoffible to be performed — by one fingle line ; it may not be amils to thew how to do it by: two lines. From A to any two angles H and B, draw the lines AH, AB, forming the triangle ABB, this be- _ ing caft up, amounts to 338000 iquare links, which is lefs than the quantity required. To the next angle C, draw AC forming the tris ~ angle ABC, which being cat up, amounts to » 322500 fquare links ; which added to the triangle AHB, gives 660500 fquare links ; which are fil lefs than the quantiry required. | _ Tothe next angle F draw AF, forming the tri- argie ACF, whole content 280800 fquare links, added to the preceding triangles AIWB, ABC, gives 9413003 which exceeds the quantity required by 158175 iquare links ;: now divide this excefs 158175 by 292, half the length. of the perpendicular EA, lay the quotient 541 ‘from F to D, and draw AD; and fo will the lines AH, AD, be the partition ines required ; and the figure AHBCD wiil contain the given quantity which was to be laid out. * E 2 SEC ith x PSS Stud h se SE. Cush oa. The ufe of the Theodolite exemplified in Surveying eve , ral parcels of land lying together, with the form of ] a Field-Book. Ae TER a general defcription of inftruments q and their ufes, fome practical examples are ne- cefiary to illuftrate and explain the particular varieties 4 which often occur. The following example is ‘ielivicell lin Gey Ee s method which at this time is commonly practifed. - The inftrument ufed in this furvey is a Theodolite q : numbered on the limb from the left to the right, and in the box (which is fixed to the index) the fame way ; — the eye being fuppofed in the center. The Chain, the Off-/et-Staff, the Arrows, &c, are as defcribed in the third Section. In one end of the Off-/et-Staff, it will be conve- nient to ferew in a piece of iron, having at the end a kind of fork, whoie legs fhall be juft “long enough to embrace the hand-ring of the chain, which being put in the fork, the end of the chain may be thruft through a hedge by the means of the Off-fet-Staff, to dive leader oh the chain on the other fide of the hedge. °° The field-book may be divided into three columns. The middle one contains the feveral lengths taken % Ptlich are to be met.with in the furvey. mark © is denoted a ftation; by Z an le; and by 7 an outfide angle: by (B) is bearings by Jn. the cutting a hedge by hain ; by ag. fome remarkable objeét on the her fide of the hedge. Thefe Aa are ufed cat, exprefs e bree. ing thus provided, in the firft sane of the field- ok, near the top, enter the title of your furvey : hen having fixed the in{trument in fome convenient place, as A to begin at, l enter in the middle co- ep the | mark © 1. denoting the firft ftation. Here obferve, that I always chufe to work in a Pate as often as opportunity prefents, _ © The inftrument being planted at A, I fend a fta- tion ftaff forwards in the lane as far asI can fee di- a — ftinGly, the farther the better, fuppofe to (B 3.) and x when I work in the land, I fend a ftation-{taff to the next eminent bend in the hedge, or even to the far- ther end of it, if the line font the inftrument to the ftaff be not at too great a diftance from the hedge, fo as to caufe off-fets greater than achain, or a chain anda half, or thereabouts. For off-fets sen too great, produce fome uncertainties, | | Then I obferve the bearing of the line AB, thus; the flower-de-luce in the box being towards me, I direét the fights to B 3, and then find the needle cut 327°, which I enter in the middle column under © mutous, 6 327°. Note, By the inftrument ufed in this example, the bearing is accounted from the north, weftward quite round to 360°, . The obfervation being made of the line’s pofition, which I am about to meafure, the next thing is to lay 3 the Py et, ee \ (54). the chain from this ftation A in a right line ~~ the next ftation B 3 3 which being done, Tet it | length ; ; viz. I areal the dittances Bi the chain from the brow of each ditch, which I enter in the - outfide columns, that on the right hand of the chain in the right hand column, that on the left in the left hand column 5 and Alp the names of the a fome of thofe which I am sane to furvey, | ie enter the names of them ; .and in all sae aspects to wich land the hedge belongs. Be Thefe precepts will not be renedtestt ‘tho? I hall 4 ever make ufe of them 3 but if any other are ufed, : : they will be laid’ down the viel ene they occur. in 4 this example, but not afterwards, Now Ienter -o in the middle column, ade 20 a in the right hand one; and 20 in the left; de- ~ noting, that at ‘no qiteaters or at the ‘efitomeAe \ the ditch on the right hand is 20 links from the . chain, and that on the left alfo 20, In the right — hand column I write William Wayy’s land, bedve to Wary; and in the left, Lord Title’s land, hedge to Lord , becaufe the land and hedge on the right is © Weary’s, and that onthe left my Lord’s. Being: now come to a, | am right againft the — fouth hedge of Hazle Spring, and alfo of Woodfield, — and there find the diftance from the ditch on the right hand to be 25, and on the left to be 20, and that afterwards the hedge on the right hand belongs — to Hazle Spring, and on the left to Woodfield. There- fore I enter in the middle column 65, and in the right hand column 25, ag. hedge to Hazle Spring, hedge to Spring ; and in the left 20, ag, hedge on Woodfield, hedge to Field. Here it may be obferved, that thefe off-fets, or diftances of the chain from the hedge, are meafured (with my ten-link ftaff, which I therefore call my Off fet =i ma a) i” P, as Vs + a ‘i Se Wi i aah re *, aa 7 d ) = oY * ns? - Bo ee ee yous oe igen) of. fet-S aff) perpendicular to the chain, and fo far till I come to that brow of the ditch, bicliis fartheft from ‘the ftem of the hedge: And that here by the brow of i ditch, I mean Bers determined diftance of ‘ 4 0 Ta lay thi be oo to have two pieces at one end of it at | iy. ee, may be made to fall into the ftaff, by {prings is Tike a clafp- knife. * Having entered thefe obfervations in the firft t length of the chain, I obferve what place of the ground is exactly under the center of the inftrument, b by dropping a mufquet-ball, or plumbing it with a ftring and weight ; then I remove the inftrument, and in that place fix, as upright as can be, a ftation- ftaff, and then proceed with the chain. And becaufe in the fecond and third lengths of the chain I meet with no fenfible turns in the hedge, nor other material occurrences, I go on to lay ita fourth time, and there againft 4¢ links I find a bend in each hedge ; where on the right hand the brow _ of the ditch is 50 links diftant from the chain, and on the left 40; therefore in the middle column [ enter 345 (denoting 3 chains 45 links) and in the right hand column 50, and in the left 40. And here it may be obferved, that I take off-fets | only at each end of fuch parts of a hedge, as run very nearly ftrait, omitting the intermediate parts ; fince when the extremes of a right line are given, that right line itfelf is alfo given: So here, though the diftance of the hedges from the chain between a and @ continually vary, yet I only take the off-fets at aand Bb, fince thefe are fufficient. But when the hedge runs on with a continued but irregular cur- vature, I take off-fets at every chain or half chain’s length, or perhaps oftner, as the thing requires, But BK 4 when yy yr eT = ox =< r ( 56 vey ae + a a when the curvature is regular, I take its extremities by off-fets, and exprefs its nature by a fketch, in 1 the : outfide columns. E In going on from 4 towards B, when I am come a toc, the chain touches the brow of the left- nang Ry ditch, againft 20 ; then] afk the hindmoft man, or the follower of the ‘chain, how many arrows he hath? a he anfwers 5; then Lenterinthe middle column 520 _ (denoting 5 chains 20:links) and in the left hand co- lumn oo, denoting that the brow of the ditch isat no diftance from the chain. ‘The chain full lying, — again{t 40 links, I find a bend inthe right hand — hedge, where the ditch 1s diftant from the chain 50% links. 4 Now it may be obierved. that I frequently afk the follower of the chain, ane alfo the leader, how many arrows they have? efpecially when I am about the off-fet or other occurrence, partly to know the number of the chains, and partly to prevent the lofs of an arrow ; for this always raifes a doubt of the — length, and mutt be removed before we proceed ; and leit when a ftick is dropped, another may be picked up in its room, I always give my arrows fome marks of diftinétion. If the fum of the arrows in both my affiftants hands are lefs than ten, then the laft length muft either be re-meafured, fince it is doubtful, or elfe the furveyor muft ftep it, and thereby difcover which of them dropt it: And this, with a little practice, he will eafily do by counting his fteps, and ufing himfelf to ftride about the fame diftance each ftep ; and by Joofing a button of his coat when he hath gone as many fteps as (by experience he knows) carry him the length of a chain. And hence he may know ewactly the number of the chains, though he cannot perhaps. find exactly the odd m eafure, But. the number of chains 1s fufficient, becaufe the error by dropping arrows always falls in whole chains, In (57) Tn like. manner, at the length of juft 800, be- ufe the chain touches the right hand ditch, and is int f from the bend in the Teft hand 40 links, I er in the middle column 800, in the night hand lumn oo, and in the left 40. Then I continue on to my ftation-ftaf at B’, i tate, I find to be at the length of 825, where, be- —caufe there is no bend in the hedge, nor other ma- - terial occurrence, I enter 825 in the middle column, and under it I draw a line, denoting that this length, and all the occurrences therein, are obferved and entered in the field- book. ~ Since [have endeavoured to be a and eafy in this firft length ; fo fhall I, in the following part of this example, be as concife as may be, sree where fomething arifes not before fpoken of ; referring the reader rather to the field-book and explanations, than tiring him with repetitions. Being come to B’, I there fo plant the inftrument: by help of the plummet, that its center is direétly over the hole, which the ftation-ftaff ftood in ; and I fend my ftation-ftaff forwards, as far as I can con- yeniently fee it as toC. Now with the beginning of the degrees towards me, I direct the fixed fights back to the ftaff at A, and fcrew the inftrument fatt: And then with the Flower-de-luce towards me, I direct the index to the ftaffat C; and there find, that the end of the index next me, cuts 202° 457, and the fouth end of the needle points at 304° 15’. Therefore I enter in the middle column of my field-book, © 2, and un- der it Z 202° 45’, and next under this B 304° 14°; denoting, that at the fecond ftation, the angle made, is 202° ae: and the bearing of the gFCOnG length is 304° | But beta I proceed, I examine thete numbers thus: To the bearing of the laft ftation 327°, I add the conftant number 180, and from the ire G07. fubtragt | ( 58 » fubtract the prefent bearing 304° 15'; and find ect a remainder 202°45', exactly equal to the angle, aa y Or elfe, to the angle 202° 45, I add the prefent bearing 304° 15°; and from the fum | 507° fubtract the conftant number 180, fo fhall the remainder 327° be the bearing of the laft length exactly, as” { taken at the laft ftation., 4 And this operation I place in the outfide Pe againft the fame angle and bearing, to fignify, ne 4 the angle and bearing have been compared, and do 4 agree, ae But if thefe numbers thus compared, do not a- gree, the prefent angle and bearing muft be ex- amined and corrected 5 and if, after fuch examina-. tion, they do not agree, there is an error in the laft. bearing, which may be taken again ; thus, 4 The inftrument ftanding in the fame place, I ac, a rect the index, the Flower-de-luce being from me,. to the laft ftation-ftaff at A ; ; and then will the fouth end of the needle point at the fame degrees which it did when the inftrument-ftood at A, and the index, was directed to B+. . Having thus taken, entered and examined the angle and bearing, I proceed with my chain, and find the lengths a and occurrences to be as you fee them in the field- book, i Then fixing the inftrament at C, as before fhewn, obferving always to fet the plate horizontal by the help of a fpirit-level, or otherwife ; I fend a ftation- ftaff forward to D, and obferve, enter, and prove the bearing and angle atC; and then ftretching the chain towards D, | find at the length of 250, a gate on my right hand, and at 260, at the diftance of 10 links, the corner of Hazle-Spring. Therefore in the middle column # enter 250, and right againft it, in the right hand column, I write Ga/e; again, in the middle column, I enter 260, and right againft it, in eh PAS hl ee ia a ee at ithe curd ation D, I do not go up the ards E, but turn off towards [,; in order in Hazle dls and. ee Bee ; sek ob- nd f facil as Pole ‘Therefore having fenta ftaff to L; Tobferve, en- er and prove the angle and bearing at D. Here it maybe oblerved, that when I came to K inthe firkt length, the. hedge on the left hand be- | es Pisa to Woodfield, and not to the lane; and there- fore I enteredin the lefthand column, Hedge to Field ; and fince this note, the hedge on the left hand hath continued to belong to the pine Woodfield ; theréfore J have not repeated that occurrence. But in going from DtoL, atthe lengthof 15 links, I am againit . the corner of Long Mead, and 10 links diftant from it, and then the hedge belongs to Long Mead. Ga Therefore after © 4. 7 259° 20, B 261° 10, I en- ter in the middle column 15, and on the left hand 10 Corner, then on Long Mead, then Hedge to Long Mead. But becaufe on the right hand we have ftill Haze Spring, and the hedge 1s 5 fill to the Spring, and be- -caufe thefe have been always on the right hand fince I firft entered them; I go on without any farther remark, till 1 meet with a different occurrence. Being come to L, I obferve, enter and prove the bearing and angle, and then proceed to M. AtM I obferve and proceed j in like mannertoN., But at N, the feventh flation, inftead of going on in the line, I proceed to clofe in Hazle Spring, and there- fore fend a ftation-ftaff to O in Spring Clofe. Therefore at the feventh ftation N in the lane, having obferved, entered and eS oved the Angle MNO, MNO, and the bearing of the line NO, “and atther Ye the chain from N towards O; I find the chain cuts the brow of the ditch at 10 fink ‘diftant from N therefore in the middle column I enter 10 /ut. denot ing the chain’s interfecting the hedge, and then] write Jn Spring Clofé, denoting that the land we are in is called Spring Clofe; and in the right hand CO ba lumn, but the next line, I write Hazle Spring, and — under this, Hedge io Spring, denoting that the land | on our right hand is Hazle Spring, and that the ~ hedge belongs tothe fame. Then I proceed toob- ferve, meafure and enter thofe occurrences as they are found in the field-book, till I come to O. : At O, I obferve, enter and prove, and proceed as ufual towards Q ; noting that at the length 720 the chain did cut the hedge i in the very corner of the _ fence ; and therefore enter in the middle column 720 Int. and in the right hand column oo Corner, and then in the middle column IJ write, Jz William Weary’s Land; and {fo proceed to Q. Being come toQ, the ninth ftation, I fend a fta- tion-{taff towards A ; and then obferve, enter and prove my angle and bearing ; and fo proceed with the chain, entering all occurrences, as in the field- book ; till coming to the length 830, I find myfelf right againft the corner of Hazle Spring, and 43 di- {tant from it; which being entered as you fee in the field-book, I write in the middle celumn * Clofe -Hazle-Spring, denoting that the extremity of this off-fet coincides with the firft off-fet taken to Hazle Spring. Having thus compleated Hazle Spring, 1 return ~ to N, my ftation in the lane, according to that ge- neral rule I always obferve, of working in a lane, and according to that rule of clofing as often as pof- fible. Now, turning back the leaves of my field-book, I find the. ftation, immediately before my coming ‘ into was by number the Guanie field-book, I enter © yf on 9 return to the fame flation: before I leave it, I t Ce RE DTP TE Santee ee REN a Kaew Gey eee ee Pacer aie te Se se eae SA mae = , 5 ons re ee a ety oe St era Tare yer oh gees aes | pat Gas) : any method of keeping a Geld-book, which lays a° & burthen on the memory, or by hich a perfon re- mote from the land, cannot plot it, is imperfect, and ought not to be practifed, | Burt it may not be improper, to ae arate the rade that thereis one thing abfolutely neceMary to be taken notice of, in obferving with any of the foregoing inftruments, viz. that the plate muft lie always parallel, or very near paralle] co the plan of the, horizon. Likewife, he ought to allow for the difference Bectiéen afeending and defcending lengths, when Be “compared with the horizontal length. For it is evident, that the length meafured up an afcent, or down a defcent, will be always greater 4 than the horizontal lengths, which only are the mea- fures that ought to be entered, either for cafling or ' for drawing the plans of any parcel of Jand wh hatfo- ever; fince thefe afcending meafures, if laid down, _ would crowd the adjacent ones out of their places. And fince thefe things are required very frequent! Ys many times in going upon one afcent, and confe- quently ought to be ‘performed 3 in the field, in order to make a proper entry in the book; I would have the practitioner be provided with fuch a T. becdolite, as will perform without compafies, rulers, fectors, ‘tables, €%c. thefe ufeful practices, or without any ‘further obfervations than what is required to take the angle only. Such Theodsdites may be made, not Only to perform thefe, but alfo to thew by inipec- tion, the height of any ftanding ftick of timber, without any calculation, tho” the - ftick food on level, _ fifing, or falling ground: Or the length of any arm out of reach; or height of any ftceple or hill: Or | by it a level proper for the conducting of water ; very ufeful for all furveyors in general. | Tho’ I do defign to’ give a {pecimen of this improved inftrument, hereafter, in all its i con- ‘conveniencies, I could not pafs it by in this place, (66 ony, = left the reader fhould over-look it. _ Jn this place it will be proper to obferve fome pat- ticulars which experienced furveyors have found ne- ceflary. In taking the Theodolite thro’ a hedge, it fome- times happens, that a thorn or fprig catching the horfe-hairs in the fights, breaks them ; therefore the © furveyor fhou'd have fpare horfe-hairs ready, and a piece of dry ftick to cut to a fharp point, to fix frefh horfe-hairs to the fights. In running the chain along a field where are many furze-bufhes, thorns, or other fhort ftuff, (or by other accidents). the links will be frequently bent, | and the rings opened, whereby the chain parts ; in fuch cafe, a fmall hand-vife, and a pair of nippers Ds; fhould be ready, that the chain may be put together again, the rings clofed, and the links. ftraitened: And. left fome of the links fhould be broke, or the rings loft, there fhould’be fpare links and rings at © hand. One of the chain-men may eafily carry.thefe 7 articles in his pockets: And it will be properthat one of them fhould every evening, or the morning — before he goes into the field, examine the chain from end to end, and rectify what may be found amifs, In cloudy dark weather, or towards the even- ing, the ftation-ftaves cannot be eafily feen, unlefs at fhort diftances ; and as it is much better on all accounts, to have them at long diftances when that can be had, andisa lofs of time to fet intermediate ‘ftaves ; therefore if pieces of tin, or other white marks were ready to fix to the top of the ftaves, the furveyor would find his account by fuch precau- tions, It apper et sd a rain, mift, dews, or ‘your breath ; ng this off to fee the needle, the glafs by bed becomes electrified, and thereby ats) t by touching the glafs with his Anger wetted, the place to which the point of the. needle ad- 4 it will be releafed from the electrical attrac- cd AR Pautitious farveyor will not leave the fe 1d for a finall, mizling rain ; and altho’ he cannot then write in his book with ink, yet his obfervations may be entered with a black:lead pencil, and thefe wrote over with ink when he returns to his abode. There are “feveral things that occur in a furvey, -which cannot with convenience be entered in the f ield- book by the foregoing directions, fuch as, “places where are many ~ buthes, pits, or other ob» itions where the inftrument and chain cannot be eadily directed ; alfo the fite of houfes, barns, ards, aoe ee Such things fhould be en ares 4 pofite page, and fuch lines meafured with the chain or off-fet-ftaff, as are neceflary to furnifh the means of pakiie a true pen thereof, ey ; shige NON «ch Sore _ Obfervations ne needle, prevents its free. motion: It rh ay ( 68 ) 4 | ~ a HOR: CLLRS ELSE -Obfervations and Dimenfions of Lands lying in hon ¢ Parifh of —-—-— in the County of - Part t¢ the Eflate of February the 2d, 1725. ; Beginning at the lane leading from¥ardly to Roughton. ‘ On Lord Title 20 O © I B 327, fefo) Hedge to Lord Hedge to Wary ag, Hedge 201 65 ' |25 ag. Hedge On Woodjield On Hazle-/pring Hedge to Field ; Hedge to Spring 490) 345 {5° | OO} Azo 540 40 00 825 F 3). Bir, 327, 00 | 180. 00 iz 507. OO 7 202.45 304. 15 B 304.15 202. 45 15}. 240 250. 2g 20 On Will. Wary > | 304. \ ERE BILE GE TTP ¢ Ge )- ee if 03 _ 304. 15 ; 108 ° ’ eee ie £.143-45 484. 15 : 340. 30 B ot eka be 143. 45 250 Gate le “ihe 260 10 Corner : ZO ZIPS). ae ee r 180 all K 4 520," 30 be “7 259. 20 tes B 261, io 259. 20 Corner 10 15 - On Leoaz Mead Hedge to Long Mead 261. 10 180 441, 10 284,-20 156. 50 284: 20 ' 180 464. 20 : Spr: 3° B 2572 30 206. 50 : \ lro againft Hedge On Spring Clofe” | Hedge to Spring Clofe | : 10] 230 240 Hg 257 ( 70 ) he RO7 Sey. 30 Ph Orns 437> 30 “7 264. 30) | 173 B 173.00 264, 30 40 Int. 4 \ In Spring {Clofe On Hazle Spring Hedge to Spring 195° 289 3 | 245 |15 173, 00 © 8: “fh 180 Y 202,15 253.000 4B 150.45 150. 45 202. 05 sl 54 < ied 335 ge BOO tues 3 720 Intioo Corner InWilliam\| Wary’s \Land $e Fs 150. 45 oD 180 “7 24.0. OO 330. 45 B 99. 45 99:1 45 oo ee ) 510 ~ [05 enc hnA 640 |70 155° Pagg 830 |43 Corner * Clofe| Hazle \Spring Taken x Land |Hedge to Spring Clofe 300 + ={100 340 |10 370 We Se i ye q Bs a mS F 4 208 iis j aes aoe hea a - s) : fi ‘1. a ue eee a Cb me nn SNS ba am LL fe hs 2 ay pan a8 JEN ya a : Tea hah eh ‘ | | | | j 340. 30 180 520. 30 LOD G |B 353.15 > On Woodfield 10 10 Corner ie a : _ Hedge to Woodfield \Long Medd - >. forse Hedge to Fs Mead Gate 20} 440 loo bg “ er tem am nene s { r e 1 353-15 180 533. 15 $2. 00 451. 15 360 QI. 15 82. 00 180 262 163 99 163. 00 180 343 93-15 249. 45 orc Rae Rt 013 he. gt. 45 |B 82. oo! 20 Int, rs In Woodfield 20 15 Corner of Hazel- (Wood Hedge to Wood 550 15 © 14 Z. 99. 00 {B 163.00 tt -@0-- J10 Gate On We aod-Clofe Hedge to Woodfield ee GO O15 7 249-45 B93. 15 35 00 Corner 430 130 600 WO ete 610 = 150 againjt Hedge and Corner of Woodfield. On Lord Title’s Land Fledge to Title 835 10 Corner 95 againfi Hedse On Hazle Wood Fiedge to Wood 20 TS vais ee \t5 Corner — @ 904 Z.180,00 B 353-+15|Oa Long Mead [Clef Weofita 20 Hedge to ditte * 140 loo Set kik O18 ‘ " 7 182.45 . Bi 220; 30) 360 © a6 445 [20 350. m B07. 40. oh. ROO nensnns 182. 00 360 py eed Bee . Gate. 75, . bo if “A Saat 4190 againft Hedge 201 215 |o0 On Butts Chfe © | a Hedge to Clofe “oo] 450. |20 SD ey” - qth Be Vs t } & Z°7 ——— Cees Aa atone Se © 21 307. 40 180 | 7 200. a 487. 40 B 287. 00 287, OO 200. 40 | 20] 50 20| 260 FAN PFS 1 380, |Gate 70] 490 E ; |00 againft Hedge and — \Corner of Long Mead OnWalter’s Meadow 9 5 sho 287. 00 R © 22 180 “7 280. 40 467. 00 B 186. 20 186. 20 | 10 {nt 280. 40 In Walter’ Meadows ; 24 110 Corner On Long Mead | Hedge to Long Mead 360 15 | 540 190 735 10 | 186, ° ! 186. 20 180 366. 20 166. 15 200. OF Corner 10 On Trout Beck Common Mead 06 10 10 River 40 166. 15 180 340. 15 IIr- 235. 15 10 ) 20 River 50 00 - 9 5 River 40 III, 0O 180 291 229. 20 61. 40 30 30 25 10 105 In Long Mead Flere Trout Beck River becomes the 251. 20 ate : Ley ae 180 3 431. 30 ; ZALT ook. 290. 30 — B 290. 30 141. 00 a on oe River 30 70 River goes off at, \this place i pie ‘he ' ‘ ‘ he es ‘ yt oe Mie P t 4 i ean H ‘ © ra om " 4 mis ; : 4 vA ‘ iw) bya) wre. ie 2) ¥ - 5 rae . ¥ TE | f p See Pete ; < “ eee ras 4 4 cS me, | ‘ : 4 , y ¥ i "; rr eo ES FOES 299. ‘sien On But’s Clofe Hedge toChfe 86) 230 ( 80) e £ O 30 2.10 ae 180 Z. 89.00 182. 10 B 93-10 93. 10 oe 65 Int. “T9. 00° In\ But’s Clofe : On Roughton Com. 100 | 65 Hedge to Clof : 350 100 | 750 ° |100 835 15 93. 10 Rl © 31 180 Z_106, 00 273. 10 B 167. 10 , 167. 10 o {20 Ou Home-Clofe et Hedge to Home-Clofe . 590 15 167. 10 © 32 180 | £126.40 Bi ie B 220. 30 220. 30 © pee : = 85 10 againft Hedge 120. 40 On Hazle Wood Hedge to Wood AIS {oO clofe But’s Clofe 3r Z.180, 00 8 93. 10 20 Int. \Gate | In Home \Clofe On Roughton Com. 195°) 1g 3 195. 175 7 BOT tre 93° egeseh sill 3 ra ne Oe ca wal 410 a O73. 10 he 180. 30 "92. 40 180. 30 180 360. 30. 238. 20 122. 10 238.20 180 3 418. 20 308. 30 —————— 109, 50 | (81) Ri 9 33 a ts 92. 4 B 180. On Mattle Mead oo = | Hedge to Home clofe 625 15 againft Hedge | On Hazle-Wood | {Hedge to Wood 7350 ee © 34 Z.122. 10 B 238.20 | oO 10 310 = {10 © 35 Z.109. 50 B 308.30 00° LO ‘ ASar IG | clofe Home-Clofe Taken from © 311 © 33. yea ZATI. 10 B 102.00 20 Int, In Mottle | Mead 300 «= |Oz Roughton Com- 315 25 (mon — — G 102. On La. Titles ‘Land Hedge to Lord — 255 [50 | co ©6130 On Hazle Field | Hedge to Mottle 295 135° (Mead 605 | \15 Corner a 620 ; ies 2914 56 180 451. 50 183. 00 268. 50 In On Hazle Wood Hedge to Wood 25 Corner 10 799 © 42 7 268. 50 B 183.00 15 Int. Hazle 375 760 15 againft Hedge On Hazle Wood ledge to HazleW ood HS clofe Mottle Mead ee Field 183, ee ( 84 ) aa © 434 183. 00 exe 180 Z.153. 30 363. B 209. 30 209. 30 efi Sole 553+ 3° Corner o0| 445 Int. In| Wood |\Chfe 25 650 Corner of 30 ~ 860 Hazle Wood | ana Woodfield ! Taken from © 38} ©39 201. 50 7 196. 35 180. 'B 185.405 oN 381. 50 i ev ree “186.15 I sal Field Sen n AZlé 1é 193+ 35 On Ld. Title’s Land Hedge to Lord 400 165 365. {100 1100 10 © 44 Oy we ary ‘7193-45 165.15 IB ra. 30| 4180 200 {ITO 305. 15 345 30 Li Lorao 4.40 7Q 193.45 BE ey 3, 785 a i © 45 apts 30 ° j 180, jz. 81.00 351. 30 279+ 3° 270. 30 $1 15. 45 On Wood Clofe Hedge to Wood Clofe 100 = 65 ¥ 3405) 19 ; 650. 75 740 {80 999 8413 270. 30 | +80 | Fis 46 | ee 412,90 450. 30 | 338. CO {3 33408 3 112. 30 Soles . z 200 1164 ag. Hedge clofe Hazle Field On Hazle Wood O45 |. “7 180. 00 B 171.30 | 1 «5 |10 Corner 35 Int, \On Ld. Title's Land Hedge to Lord In} Wood \Clofe 255 3° | 300 G 3. 171. DONA Ne Bi wach. 20 againft Hedge Woodfield = — afer” 2; SECT. VI, % 0 To protrast the obfervations contained in the preceding Field- Book. IRST, draw parallel right lines, as thofe in Plate I]. marked NS, reprefenting meridians er north and fouth lines, at a diftance from one an- other, not exceeding the breadth of the Gameiricn part of the Protracor. | Then picking out fome convenient Bees to repre- fent the firft ftation, as A ; the field-book being open before me, I lay the center of the Protractor on the point A, and the diameter parallel to the lines NS, and the beginning of the degrees down- wards, becaufe the bearing is more than 180 ; ; then againit 227 degrees, I make a mark with my Pro- tratling Pin, to which J draw an obfcure line from A, reprefenting the chain-line from the {tation A to che {tation B. Then to this obfcure line, I lay the ode of my Plotting Scale, the beginning of the divifions co- inciding with A, and “increafing towards the next {tation B, and eae the off-fets, inthe firft leneth, are taken at the diftances 65, 345, 520, 540, 800, 825 ; therefore, again{t thefe numbers on the {cale, I make marks in the obfcure line clofe to the edge of the fcale. This done I turn my fcale perpendicular to the obfcure line, and apply it fucceffively to thefe feve- ral points, and there prick off the lengths of the fe- G 4 veral See " 1 tee ( 88 } | ral offfets on their refpective fides of the obfcure line, fo at A, I prick off 20 on the right hand, and 20 on the left; at the length 65, which is the next point, I prick off 2g on the right hand, and 20 on . the left ; and at the next point, which is at the di- ftance 345, I prick off 50 on the right hand, and 40 on the left ; at the fourth point, which is at the di- | ftance 520, I prick off oo to the left hand ; at the fifth point, which is at the diftance 540, I prick off | 50 tothe right hand; at the-next point, which is at the diftance 800, I prick off oo to the right hand, and 40 to the left; at the laft point, becaufe no off-fet was taken, I lay none down. And now, if lines are drawn from point to point on each fide of the obfcure line, they will reprefent the fences as was required. But when the off-fet is oo, as in the fourth and fixth diftances, thofe points, to prevent being over-looked, fhould be marked with a black-lead pencil, or fomething elfe, which may be eafily rubbed out again. At the fecond diftance, where we were againft the fouth fences of Woodfield and Hazle Spring, with a black-lead pencil draw two fhort lines, cutting the Jane, to denote that the fouth fences come up to the lane, and will hereafter be of ufe in clofing thefe lots. , 2 Having thus finifhed my firft length, J produce it, if occafion require from B, both ways, till it is as Jong each way as the Radius of the Protraéior. Then — _ I place the center of the Protraéor on B, and thereon turn it about, becaufe the degrees of the next angle are more than 180, till the begnning of the degrees of the Protraéfor are contrary to the laft flation A, and the diameter coincident with AB. Then clofe to the edge of the Protraéfor, right again{t 202° 45', I make a mark with my Protraéting Pin, and to it from B draw an obicure Jine reprefenting the chain- line from B taC, | Tnen. B ¢ 89) Then T ‘turn the Protraffor about, the center ail! coinciding with B, and becaufe the bearing i is more than 180, fet the beginning of the degrees towards S, | and the diameter parallel to the meridians ; ; and then, if you have truly wrought, the line BC before drawn, will meet the limb of the Protrattor again{t 304° 15), the bearing of the line BC. ie But if it doth not, the line BC is not in its true F. ~ pofition, and mutt be corrected before you pro- ceed. Or thus; the center of the Protraffor colficiding with B, I turn it about till the beginning of the de- grees is towards S, becaufe the bearing i is greater than 180, and till the diameter lies parallel to the me- ridians ; and then clofe to the edge of the Protraéor, with my Protracting Pin, I make a mark againft 304° 15, the bearing ofthe line DC, and toit, from B, draw a ftrait line reprefenting the ftrait line BC. Then turning the Protraéfor about on the center C, and becaufe the angle there taken was 202° 45', or more than 180, I turn the beginning of the degrees of the Protragfor contrary to the laft ftation A, and the diameter to agree with AB; and then will BC meet the limb of the Protraéfor againft 202% 46 sit the bearing is truly down. And thus the plot may be laid down by the bear- ings, and examined by the angles. ‘Then to this obfcure line, 1 apply the end of my Plotting Scale, the beginning of the divifions co- inciding with the prefent ftation B, and the num- bers increafing towards the next C ; and then clofe to the edge thereof, againft 240, 250, the lengths where the off-fets were taken, I make marks with my Protrating Pin. ‘This done, I turn my {cale perpendicular to the obfcure line, and at 240, I prick off 15 tothe left hand, and againft 250, which gives the point C, J prick off ro the right hand, as the field-book directs, Now continuing the fences to ' | (90 7 : to thefe off-fets, I fhall have finifhed the fecond length from B to C. The fecond length thus finifhed, I produce it, + otcafion require, from C both ways, till the length. each way be at leaft equal to the Radius of the Prow itrvaéior, Then I place the center of the Protragfor. on C, and becaufe the degrees of the angle at C are Jefs than 180, I lay the beginning of the degrees of > the Protraétor towards B, the laft ftation, and the diameter on BC. ‘Then clofe to the edge of the, Protraétior, with my Protraéing Pin, 1 make a mark againft 143° 45', the quantity of the angle at C, and -toit draw an obfcure right line from C, reprefenting the line from C to D. Then turn the Protrafor etine its center ftill co- inciding with C, becaufe the bearing is more than 180, the beginning of the degrees towards S, and the diameter parallel to the meridians, and then if you have worked truly, the line CD before drawn; will meet with the limb of the Protracfor againft 340° 30', the bearing of the line CD. 4 But if not, the line CD is not in its true poles | and mutt be corre@ted before you proceed. From the laying down thefe two angles and baie ings, it appears how errors often happening in prac- tice, may be prevented. 2 The general rules I obferve herein are three, viz. 1. I lay the diameter of the Protraéfor on that ~~ line which brought me to the prefent ftation, where ¢ the angle, about to be laid down, was taken. 2. I Jay the beginning of the degrees of the Pro- traéior towards the Jaft ftation, when the angle is lefs than 180 degrees ; but the contrary way, when the angle 1s more. ri nD e : ie | gr ) i ! igs ogc arte gia v i, Mr laying down or examining the bearing, 1 ‘a the beginning of the degrees of the Protrafor northwards, . when they are fewer than 180; but fouthwards, when more. — “Yn like manner I lay down and examine the angles. | snd bearings taken at D, LL, M, N, O, Q, the 4th, sth, 6th, 7th, 8th, gth Batons: and ‘alo the cor- refponding lengths and occurrences. But in the laft length QA, having at the length 830 laid off an off-fet of 42, it gives exactly that corner of Hazile- f ring, which was noted down in the firft length in e Jane; which proves that the angles and lengths fnclofing Hazle-{pring, are truly laid down, But if the extremity of the laft off-fet in the length QA doth not coincide with the extremity of the fecond off-fet AB, both denoting the fouth weft corner of Hazle-fpring, the lengths and angles defigned to in- clofe the fame Hazie-fpring, are not truly laid down, and therefore muft be examined and corrected be- _ fore you proceed. Now © 7, being marked with 7, anumber not greater than 9, ‘the number of the lafl ftation, be- ing the next work noted in my field-book ; I retura to © 7 1n my. draught, and there with MN, the line which I meafured immediately before I came to N, Imake the angle MNR 162° 45,, and the bear- ing NR 274° 45, as noted in the field-book, and then proceed to lay down the off-fets and other oc- Currences, at their proper lengths and diftances. Having finifhed NR, I find next following in my field-book .© 10, which becaufe it is greater’ ‘than 8, the number which immediately follows 7, the num- ber of the laft ftation; and becaufe I find no ftation already laid down, marked with a number fo great as 10, therefore I eencliles that the ftation R, vier I now am, is to be durabred 10; and from thence proceed proceed to lay down ( 92 ) bearing at R, as ufual. The rules I obferve in thefe cafes are, 1. To erates with black lead all the ftations I | have already laid down in my draught, and alfo to exprefs thofe numbers fucceffively after one another, in a piece of wafle paper, which I examine as often as J pleafe. | | {a 2. If I come to a ftation whofe number doth not jmmediately fucceed the number of the laft ftation, but is greater than the greateft of thofe numbers noted in my wafte paper by an unit; then at the fta- tion now. arrived at, I lay down and examine the bearing and angle with the line I meafured imme- diately before I came to this ftation. And this fta- tion I number as denoted in my field-book. 3. If lcome to a ftation, whofe number doth not immediately fucceed the number of the laft ftation, but is greater than the greateft of thofe numbers noted in my wafte paper by more than an unit, and examine the angleand . Ns ae then fome omiflion hath arofe in my wafte paper, and mutt be rectified before I proceed. 4. And laftly, if I come to a ftation whofe num- ber is already entered in my wafte paper, then I re- turn to that ftation in my draught, and there lay down and examine the bearing and angle with the . | line, meafured immediately before I came to this ftation, the firft time, Now the next obfervation I meet with in my field- book, is again © 10; therefore again at © 10, I lay down and examine an angle and bearing, as noted in the field-book, and then proceed to lay ~dowa » ( 93 ) 7. the lengths and off-fets of the line RS, as I oy find in my field-book. Being come to S, I proceed to T, a from T to ° P, there clofing with the extremity of the off-fet at _P, coinciding with the fouth-weft corner of Spring- clofe, and the fouth-eaft corner of Haz/e-/pring. This done, I find next in my field-book © 4; therefore I return to © 4, and there proceed as my field-book direéts, till I come to ftation 13; and be- -caufe this is a number greater, by an unit, than 12, the number noted in my wafte paper, I number it 13, and then proceed, as my field-book directs, to F, G, H, I, and K, there clofing in Woodfield by the extremity of the off-fets there laid down. This done, I next find © 13, and therefore, be- caufe already entered in my wafte paper, I retusn to © 13 in my draught ; and then proceed as before _ fhewn, till I have plotted all the occurrences men- tioned in my field-book: But the remaining part hereof I leave for the exercife of the reader. All houfes, barns, mills, or other buildings; alfo. kilns, ftone-pits, gravel-pits, ponds, watercuts, hills, hollow-ways, land-marks, bridges, roads, bridle- ways, foot-ways, ftiles, remarkable old trees, and any other particular which the furveyor may mect with on the eftate he is working in, fhould be noted in the field-book ; and fuch meafures, and {ketches of them taken, as that they may be inferted in the plan: For fuch particulars being frequently referred to in old terriers of eftates, their being accurately _ delineated in a map, would afcertain their pofition and diftance from other places; and thereby pre- vent fome of the fatal contefts that arife ae neighbouring families. When all the particulars contained in the field- book are delineated or mapped, caft up the contents of each inclofure, road, lane, wafte, €Sc. by the me- thods before fhewn; and.-write the contents, together 4. with ee: [ee ’ ue vi ‘ ; a7 ( 94 ) with the name in each piece: Let the plans of build 7 ings be fhaded by lines drawn acrofs; and’write the names of the neighbouring eftates or parifhes on the outfide, near the places where they bound the lands in your map ; alfo at the ends of roads and_ lanes, write where they lead to and from; and thus will the foul draught of the furvey be finithed, This 7 foul draught may be transferred to your clean paper, parchment or vellom, many ways ; among which ~ the following one is eafily practifed, ANG Laie the i fcrapings of red chalk and black lead, in| equal quantities, mixed together ; rub the back of . the map with this powder, and then wipe off as much as will come away with gently rubbing a cloth — | over it: Lay this coloured part downwards on the _ paper or vellom, faftening them together with weights, pins, és¢. Then with a fharp-pointed bod- deli or tracer, trace all the lines of the furvey, and the impreffion of them will be marked on the vellom : Take the foul draught off, and go over all the co- Joured lines with a fine pen and ‘Indian ink; and fo will the draught be transferred. Annex a fcale of polesand yards; with acompafs, allowing for the variation of the needle ; alfo infert the latitude of the church, manor-houfe, or fome other noted mark ; and embellifh the map with fuch other ornaments as are commonly introduced in ~ works of this kind. Obferve that the reprefentation of the hedges ought to be laid down onthe fame fides of the fences, that they are inthe land; and to be broke off where there are to be the reprefentations of gates, Ec. There ought to be imaginary lines, both vertical and horizontal, denoted by letters placed at the top and bottom, and alfo on the fides, to be referred to by the table of references ; for the ready finding any field, or parcel of land therein contained. Laftly, C95) ~Laftly, I fhall, in this place, only add, that in all.performances of this kind, errors, for the moft part, arife from the defects of inftruments, in the framing, dividing, and contriving. ; PEC rT Vil Of a new, certain, and expeditious Method of Survey- : _ ing and Plotting by the Theodolite, as now im proved. N the practice of furveying, it hath hitherto been found very difficult to make a large parcel of land, when it came to belaid down in a map, clofe exactly with regard both to the lines and angles meafured, efpecially if it were mountainous and hilly ground, nay even a {mall quantity of uneven land has often puzzled thofe who otherwife thought themfelves ex- pert furveyors, Now this difficulty in clofing the : draught, arifes chiefly from the following caufes. . : Firft, The not taking care to place the plane of the inftrument truly horizontal or level, and which indeed it is almoft impoffible to do by the eye alone, efpecially on the fide of a hill ; and tho’ this may by ' fome be thought of little fignification, yet thofe who have any knowledge in geometry, mutt allow, that very great and unavoidable errors will arife thereby $ for it may be demonftrated, that if the plate of the inftrument dip but 2 degrees at right angies to the the line of obfervation, and the hill defcend 10 de- grees, it will caufe an error of 42 minutes in the * This SeGtion is part of Mr. Warner’s Appendix to the fecond edition of this book. angle, (96) anple, and the object will be thrown out of its true 4 place 12 links inthe diftance of ro chains; and how great confufion muft this make in plotting the fuc- ceeding angles which turn thereon as on a center ? But if fo confiderable an error arife by miffing tlie ‘level only 2 degrees, nearer than which I believe no one will pretend to place an inftrument with by his eye, what egregious blunders muft the _ practifers with the plain table make, who, when they cannot fee thro’ the fights of their inftrument on an afcent or defcent, do commonly nfe, dip, or, as it may be properly faid, twift the plane of their table more or — lefs out of the level till they can fee their objects ? Secondly, The not making due allowance for the difference between the lines of afcent or defcent, and the horizontal lines, which are the only lines that ought to be laid down ; and though it is a common practice on the fide of a fteep hill, to double the chain, and fo in afcending to make the leader hold the middle in his hand clofe to the ground, while the follower raifes the end by the ftaff in his hand, till he judges it to be ftrained on the level, and in defcending, the leader elevates the middle by his ftaff in like manner, while the follower keeps the end clofe to the ground ; yet a true horizontal line ~ can hardly be obtained this way, by reafon of the fwaying of the chain, and the uncertainty of keep- ing it in its due place. Thirdly, The plotting the angles by removing the Protractor from ftation to ftation ; in doing which, if we confider the nicety required in laying the diame- ter of the Protractor, and the variation of the hand in pricking down the quantity of degrees and mi-— nutes, and in drawing the ftation-lines, we muft al- low it to be a very difficult matter to protraét fo near as 10 minutes; whence, if there be a confide- rable number of ftations in the circuit, the plot will rarely be found to clofe as it ought, for an error in any F iC 97) any one of the angles will be communicated to all that follow, and each fucceeding ftation will be thrown more and more out of its true place, as it is farther from the angle where the error firft arofe ; and though i it be a good way to protract. hadkewards ; as well as forwards, yet even that will hardly bring it to bear, unlefs the errors ee to counter- pe. _ The foregoing are. » the principal caufes that render it difficult to make a corre¢t map ; and they are 2 ‘now intirely obviated by the New Improved Theodolite, — var 5 as made by Mr. Heats, and the method of fur- --veying and plotting hereafter defcribed. fir, This inftrument has a fpirit-level affixed to the telefcope, and another {pirit-level at right angles thereto in the box ; by means of which ctofs levels, and the help of four fcrews playing between two plates in the brafs head of the ftaff, the plate or limb of the inftrument is readily brought to a true hori- zontal fituation. Secondly, ‘Lhe telefcope with crofs hairs therein, _ turns on an arch fixed to the index perpendicular to the plate of the inftrument, the arch is of the fame radius as the plate, and the telefcope may be elevated” or depreffed thereon quite to a quadrant, or-go de- erees, On this arch are graduated the degrees of a circle, which are numbered from the vertex either way, with10, 20, &¥c. and are cut by an index un- der the telefcope, divided after Vernier’s (commonly called Nonius’s) way, like thofe on the limb of the inftrument, Within the degres are two lines num- _ bered with 10, 20, €%c. down to 100, and cut by 4 the edges of the index; om the right whereof is graved Elevation, and on the left Depreffion. ‘Thefe dines ferve to fhew the altitude or depreffion of any object in rooth parts of the diftance at which the in- firument is planted to take the obfervation, and are ufeful in finding the height of a tree in the Brune ri ) + 7 ‘(6 98") Of timber ftanding ; as alfo to find the altitudes of a the feveral parts of a building in drawing the per- fpective appearance thereof, as will hereafter be — fhewn. Below thefe are other graduations cut by — the lower part of the index, which fhew the diffe- rence between the hypothenufe and bafe of any — right-angled triangle, (the hypothenufe being always fuppofed to confift of 100 equal parts) and confe- — quently they give by infpection the number of links to be deducted out of each chain’s length in going up or down any hill, for reducing the hypothenufal lines tohorizontal. ‘There are aifo plain fights fixed upon the telefcope to be ufed in fhort diftances, and for continuing the fame ftrait line both ways from the inftrument, as is neceflary to be done in — cafes. When the index under the telefcope is fet to 00° at the vertex of the arch,.and the two bubbles brought tothe middle of their tubes, then the hori- zontal hair in the telefcope cuts an exact level, and the plate of the inftrument becomes a true horizontal plane; and if the interfection of the crofs hairs be fet to any object by moving the telefcope above or be- Jow the level, the divifions on the vertical arch will fhew the elevation or depreffion of the object: Alfo, when the telefcope is directed to any object, the in- 7 | itrument may be readily fixed fo firmly in that di- rection, by turning a fcrew under the center, that © there can be no danger of being ftirred by removing 7 the index on the plate towards another object. The ~ degrees on the plate are divided fo accurately, that — though they are cut by three indices 120° diftant from one another, having Vermier’s (or as vulgarly called, Nonius’s) divifions on each, yet the eye can perceive no inequality in the divigions all round thé limb, but whatever part of a degree the index under the eye glafs of the telefcope cuts, the fame will al- ways be found to be cut by the other two; thereis I alfo 4 4 oa. (55) alfoa a finall Rides that cae to cut the particular dis vifions s on the limb to be uféd for taking the breadths in drawing the perfpective appearance of any build- 4 : earn whole index, with the box fixed thereon, turns round ona conical center without ftirring the ne edle, and may be fixed to any part of the limb, _ by means of a {pring and fcrew adapted thereto. li ‘a word, the entire inftrument is contrived fo com- holes, portable and {trong in all its parts, that it is allowed to be the beft of the kind ever yet made. __ Thirdly, In order to avoid any error that may a- rife in taking the angles in the field, or from pro- tracting them angle ‘by angle, as has hitherto been the univerfal cuftom, let the furveyor obferve, this following method, which for its readinefs as well as accuracy, will, no doubt, be preferred and practifed by all who would excel in this art. The inftrument being planted at the firft ftation, ‘fix the index to 360 degrees on the limb, and fett- ing the plate truly horizontal, turn it about till the fouth end of the needle hangs over the Fleur-de-lys, or 360 in the box, and fix it in that pofition by help _ of the {crew underneath ; then difcharging the index, turn that about, and direct the vertical hair in the telefcope, to cut the fecond {tation ; there fix the index to the plate again, and the fouth end of the needle will fhew the bearing of the firft line, which will alfo be cut by the index on the limb, and is to be entered in the field-book, as before fhewn. Now when the inftrument is removed and planted at the fecond ftation, obferve that the index hath not been fiirred, and turning the whole limb about, direct the vertical hair in the telefcope back to cut the firft ftation, fix the platein that pofition ; then difcharg- ing the index, turn it about till the fame hair cuts the third {tation ; there fix the index to the plate again, and fet down the nuinber of degrees and mi- nutes it cuts on the limb, which number will at the H 2 fame ( 100.) 4 fame time be cut by one end or other of the needle in the box, if there be no miftakein the obfervation: _ Proceed in like manner at the third and all the fol- _ lowing, ftations, always remembring after you have turned the plate about, and directed the telefcope backwards, to obferve that the index remains fixed at the decrees laft noted in the field-book, fo will % the needle be always found to correfpond with the q index fufficiently near, to difcover and prevent any error in the work, We have here added an example of part of the field-book of an actual furvey, wherein the angles were obferved by the method above defcribed; and though there were 24 {tations in the circuit, yet for proot, the inftrument being planted again at the firft ftation, and the telefcope directed back to the 24th, the plate being fixed in that pofition, the index was difcharged, and the telefcope direéted to the fecond {tation, and then the index cut the fame number of deerees as was firft fet down in the field-book. When there is occafion to return to fome former ftation, in order to go off from thence for the clof- ing fome particular part, as in the following ex- ample, we return to ftation 23. Enter the number of fuch ftation again in the field-book, with a {mall figure at the fan of it, denoting hie often the in- {trument has been planted at that ftation, thus 237 denotes the fecond time of planting the inftrument at {tation 233 then confider from which itation you~ : locked forwards to the prefent ftation 23, which was ftation 22; feek in the field-book the bearing of the line between the ftations 22 and 23, and fix the index to that number on the limb; then turning the plate about, direct the telefcope back to the former {tation 22, fix the plate in that pofition, and dif- charging the index, direét the telefcope forwards to the next ftation, and thence proceed as before ; fo will the needle be always found to bea fure cheque on Pa, v Hox”) © a 4 on "he imb, tho’ the obfervations do not depend ye thereon, ey The letters affixed to the numbers of the ftations in_the following field-book, are not to be -ufed in praéiice, being here added only for the more eafy referring to the plot, in defcribing the new method of laying down. Betinber ‘slows’ it, it means that both the numbers f ; i. to be laid off on the off-fet line. 2, fignifies an angle or corner. a Bs FIELD- F LELD-BOOK of Part the Manor of RB » Ga Remarks, Left. Renciie - + oie , « = Hedgebuts to Kiln Wood 20, Againft Kiln Wood - -| 27 Hedgetoditta - - -| 3% 2. + laff Bearing - |- - -\204:40 ; 30,175 15 280 301 400 : 21} 560 Hedgebuts to Furzfield 14 746 | ges, : © 3 (©) Againft Furzfield - - Ve Fern) | Re rete oe. I 100 31 200} 21 305 (44610 far clofi ing Furefeld and 4g Hedgebuts to Furzfield Ne, oo aa”, A Lang re againfi upper Poundfiel Bie) 5201 . . | 0 4(D) 19550 | 46} 140 | —Hedgebytsto WoodsGa| 41 255 Depth of the Gard. 216 Pound begins, andFence-| 48 500 buts ends 46 527 \ J 8) toGareinto lower Pound oe" ahi } : nd field, | Woods Houfe 3 30 deep } ‘ é ; B . | : | : ae ar 2h Hedgebuts to Lower | PB Bp of Woods Garden| 2A) 272 | Poundjield againfe E. ; 113 deep, and Hedge 300} 32 Pondjield. Zz «buts to upper Pound- ! ! a: field ua’ \aege e 201 350 - Gate- - - - - 281/34 28318. 20 A44] 2 3!Hedeebuts toC awhou/e= J 5 465 field. : 127d eee). 25 : ® 6(F) | 107350 Raid = Toe = SM 58 2 6'Gate. Hedgebuts to Upper| 42 155 Poundfield againfi 200), 29 Hedgebuts to Ribas Little Boggyfield lige eG) > ee 238)- : -|Gate. 6" B00) j. 22 2 7(G) ee ely ae , 15 O12 170} 6 Lane returns + - - 21 186 Zr 4againfiGravel -pit- Wi . field Hedge to Barnfield - - 7 — eat dae Ep eT) go ro Osteen We 268320 50|x Gatelinto Pound Lane feld againft the Hop- 222) 16) pit. 200) forlihe Return N° 32. 247)19 XiGate into Moor’s Bare: field. 267 = Ponds begin in Gravel- pit field } Ponds end - - ~ Gap - - - = - Fence changes to Gra- wei-pit field, Gate - - - From bye ©) at 330 in Line 11, 12. } 5°}90 339123 319 to © |383|- -© N° 11. [100] 6— 280} o 315139 Ba ia Bi | 130} 4 oe 170! . 286/58 ! Ns 375)69 : 440} O -) IOl4.80 tla § 1951494 Field oS as 1568)x Hedze & Brook into} Alders 34 xGravel-pit feld Hedge 45 into Ditto, againfR Home field Hedge to P21 ditto, eS «bbl Hedgebuts to Dung field a Gate. oO Cumbers’s 698| x Bill 330lbye @lfor the Alder Ground. |FieldHedge Alder Ground. {720\f0 © 13 x Hedge and Brook inte Hedge. ‘A5\t0 Gate-+-60 to Zr. Hom fted. Go Hillyfield Hedge - - Againft Alder Ground Be To Alder Hedge 45 -- field Hedge into Boggy- Be I pans 6lx billy To Al. hedge 81-4- Corn 44 “nel. To Alders - - = - Fo Kilnfield Hedge - - To Alders een To bunting Gate 55 -+- Point of the Yland59+| 3° Cea (eahoo ays: + Aan Lland - - -| Fence toditta - - -| Corner 2 = 2 Hedge to Bogeyfield - | Wacdland ends - - 19] x |Bocgyfield Hedge to Againft Acre Bit - - 240 Broomfield. > | 74, xX Acre Bit Hedge to dit. i To Alders - + = |. 150 Oo To Hedge : ns To Hedgets-+- - - 25 -- aha t : \Acre Bit-hedge into lit-~ tle Broomfield. i 290310 e. 49 20 Again Kilnfield Gate |- - -|__ 17° 4 | 16 23 (Y)] A 104:00 en enn © 24(Z) = 7 Twi 243) x jHedge into Warley Com. To © 1 where the 1 7 from the laft Bear- ing to ©) 2 was found to be 43°:20 as at firft fetting out. lagainft Kilnfield Gate. x \Gate into woody Ground in Kilnfiela. Q25%X\out of Wood into field a | agft Kilnwd H. te dit. 324) 12 465, 26 510)" Ga 580, 72) 630] 55) i 890) ©25 (a) is 84.240 aq if 37| 18x into Posey Wood tie ‘ So} 15) 4 ditto. 4 \ 1 | 246) aap E P 3 ©26;b) | — (284: 40 i Spe We i 170; 50 i 209 x into Furzfeld Henge to dit. ; | 224! 53 i ©27 (c) it 105:30 \ | 100, 29) , : 1QO; to Corner clofe Kiln Wood. q { i Returnto- - +4 © j25* (alee - i ae Kilnfield. | . | 39; 33 again# Boggy Wood. 280] 37 é 396\- - -Hedgebuts to little Pies 4 424) gyfeld. Aa ©28(d)| : 2.52: 50 if ft 34 X Bogoyfield Hedge inte 120) 45 ditto. 7 | 200} 42 “ae Be : : : f Me Ope Waa: ele on uae eA, 100”) \O29 (e) . hs 79:30 4 catia OR ee 1OooO 35 r Strait Hedge to Pound-\- - - 161 x Upper Poundfeld Hedge “eat 190 into ditto. tig? ——!_—_— = |—— ay J © 30 (f) : ie 225:12 50, 28 : 158 x Furzfeld Hedge into dit. 187 : ©O31(g) 184:00 35) 30 Corner. | 65) 45 300 oe 5 eas 428 | 40 @\27 clofe Bogsy Wood. Return to = - =) ss) 31” (g) 100 80 fie 314] © #0 for clofing Furxfield in Ret. to© for the Re- ) -—— a5 Thy ———— Line 3, 4. turn of Pound-lane O | 32 ( ) againft Gravel-pit field at 200, in Line 7,8 68:20 Hedge to ditto. 147} 29 Hedgebuts to little Bog-) 11 212 Ki gyfield. 237\- - ~|Alders end. | 306] © 33 (1) 172:08 Stile in Boggyfield Hed.\ 110 118 7 8 390 Pond, 50} 454 28} 574 43) O15 670| to ©}28clofe little Bogeyfyld. Return ita - - o H Godel pie ‘fold H i 69 ‘into mete ee A. Gy Kilnfeld ~~ - . he hier: again | Refura face ie es va Kilnfield Gate. | Nott : x out of Wood into. Kila- 4 Againfi Woody Ground jela. j Kilnfield. Corner - + © = ‘Paffage to Iland - - - 30 50 X\into Woody Ground. By uct | 165 x|Rill. ee ; i 45 256 85 x into Land. a 120} 390 455) 80 gol 520 57O.-- VO} Corner. | 50] | 594 To the Top of the Iland. | FBciurk be on apie -| 0! (387 (0) | 357:00 $71 4 bi 181:48 X|Kilnfield Fence inte rough Ground. 451 XiGravel-pit field Hedve 473 into ditte. ©39(p)) 235:55 248 15 Railshutt +- 61 to ; rough Ground Fence. ‘a . (1Kilnhoufe 33 deep +x be 16 35 to Fence. 674126 Hi f Workboufe 65 deep. Chfe Gravel-pit field 7651 x linelz2, 33 clofe Kilnfeld. Now SRE a Rg oe PTE eer erage Pee ee ee ee ty eee er Se adiaisea ee y= > : = Se See ei i Kak =i. ako o >in oon oon . Fg eg ag eg ee a ee a ee eee cae ee ee ae ee eS oe ee ae ae ee oe yy Se = soe ae - SO ae ee — o% es a ne er Ses tn al 5 (1921) Now to protraét the foregoing obfervations, thro? the middle of the paper defigned for the draught, draw the right line NS for ameridian, Plate [I].and therein chufe a convenient point C, to which lay the center of acircular protraétor, the diameter coincid- ing with the line NS, and the 360, or beginning of the degrees being towards N the north, fix the pro- tractor in that pofition by laying a weight thereon, or pinning it down; then on the circumference of che protractor prick down the feveral bearings noted in the field-book, numbering from the north eaft- — wards, or towards the right hand all round, and to each point affix the number of the ftation to which it belongs. Chufe a convenient place on the paper foi the firft flation, as at A, and laying the edge of a parallel ruler to the center C, and the point ‘marked I, Open. the ruler till the edge cuts the point A, and thereby | 3 draw an occult line ~ parallel toC 1, on which fet off the firft length (165) from A to B, the ad ftation ; then laying the parallel ruler to C and the point 2, transfer it to B, and thereby draw an occult line, on which fet off the fecond diftance (766) from Bto C, the third ftation: Again, lay the parallel ruler to C and the point 3, transfer it to C, through which draw an occult line, and thereon fet the third di- {tance (520) from C to D the fourth ftation. _Pro- ceed in like manner all round, and if the work be true, the laft line will pafs through the firft point ; but if it doth not, and the error arifes by miftaking a whole chain or fo, it may readily be difcovered in which line it was committed by obferving whether the laft point fall fhort of, or beyond, or above, or below the firft point with which it ought to co- incide, uae The only feeming difficulty that can arife in draw- ing the ftation lines by this method, will be to di- ftinguifh between an infide and an outfide angle, though 3 al a ‘at i i ; nie } an fel ca be any obftacle to the fur- ft the dimenfions, and who by the idea the nd, will, for the moft part, remem- er he turned off to the right or left at fuch a {tation ; yet, if he fhould at any time lays work to protract, and a multitude of fhort ions therein: Or, if any perfon who never faw and, fhould attempt to draw it out by the feld~ ky and find himfelf at a lofs about the quantity of al ele; then let him fubtra& the bearing at the ae ftation from the bearing at “the pre- ent itation in queftion, increafed by 360, if fub- ae raction cannot otherwife be made, and the> re- mainder gives the prefent angle ; which if it be lefs fe ex fs than i80°, fhews that the line flowine from the fta- | ie at © 17 noted with R, ic might be doubted, + sit the line from thence fhould be’ drawn in- Fe = towards f, or outwards towards S ¢ to folve be hich, from the bearing at the prefent © 175 280° “ fe Bes fabtraét the bearing at the laft © 16, 23°: 20, _and the remainder 247°: 30’being greater than 180: a ~~ 00, fhews that the line mut be drawn outwards to- : * _ wards S 3 the fame doubt might alfoarife at © 18 (S), but if from the bearing at © 18, 347°: 50’, we fub- tract, the bearing at the laft © heel a Ss the re- _ mainder 67°: 00 fhews it to be an infide angle: ° Again, at © 19( T) the bearing is 27°: 25’, to which _add 360° , and fubtraét the bearing at the laft © 18, "349°: 50, and the remainder 39°: 35! fhews the prefent angle tobe an infide angle, and ver y acute. When the draught is fo large, that all the {tations cannot conveniently be laid down about one centre, the firft meridian line may be prolonged, or another drawn parallel thereto, in which the furveyor may Mmake choice of a new centre where he fhall think moft proper, and round this he may place his re- Maining {lations in like manner as before Hikes I an it may perhaps happen when he has {e- _ tion mut be drawn inwards, BAC rore, outwards. —e - xy ( 114 ) and thus, he may chufe as many centers as he find necefiary, but the fewer he can difpenfe wit the better. Moreover, the bearings may be laid down by § : femicircular protractor numbered, as it is commonly — done, with a double row of figures to 360°, which — fome may rather chufe to ufe, becaufe the limb_ thereof may be turned wholly towards tHe light, that | : fo the divifions may be more advantageoufly feen 5 ; but confidering the edge of a protractor is always” mace very thin, there can be no advantage gained ~ thereby ; befides the circular ove is to be preferred in‘that it hath twice the room, and confequently, — when there is occafion for laying down a great num- ~ ber of obfervations about the fame centre, they will — be lefs liable to confufion. Again, the degrees on @ the limb of the inftrument and in the box, may be numbered only to 180, and then begin again with ~ 10, 20, &%c. to 180 more, by which means that © end of the needle which is next the eye, will always cut the fame divifion in the box as the index doth on © the limb, and there will never be occafion to enter a k bearing greater than 180° in the field-book ; fo a © femicircular protractor numbered with a fingle row of figures, will ferve to plot all the obiervations ; but then there will be this great difadvantage (as wee as the foregoing in point of room) that, fhould thea furveyor forget whether any angle was more or lefs © than 180°, he could not readily difcover which to : - make ufe of ; and fhould.a perfon, who had never ~ feen the Jand, go about to protract the work from fuch a field- Bak alone, he muft be gravel’d at every _ ftatton where the angle approaches near go° or 270°, : as not having any means whereby to difcover on — which fide it is to be formed, tho’ this doubt may © in ei meafure be prevented by noting the angle ; in’ the-held by the-mane-4:, Oray. according as it~ is within or without; yet fhould the furveyor put down wrong: ak or forget to enter any (which “happen when a multitude of obfervations be taken, and the weather proves untoward) cafe a great deal of time may be fpent before -afcertained whether the angle be internal -external, which is very readily known in the for- er method ; therefore that mutt be the mott pre- ‘oins part of this book, that a farther explanation | ould be altogether needlef, 43 ngs, there never can arife any difficulty concerning _ which way the line is to proceed from the laft fta- tion ; for as every ftation line is to be drawn ina of the protractor to the direction in its circumference marked with the number of the ftation; therefore its _ pofition is naturally afcertained by drawing the line _ in that direction, f The figure in Plate 1V. fhews how the contents aot the foregoing example of part of an actual furvey was caft up; and here are likewife fubjoined the di- - menfions and calculations ; whereby it may be feen, “that notwithftanding there are 10 feveral pieces mea- tured feparately, yet when the whole plot was reduced to the trapezium: MNOP equal thereto (by Prob.10. page 8.) the content of this trapezium was found not to differ from the fum_of the feveral contents by half a pole, a confirmation of the truth furprizingly “near, | | , I 2 Gravel- ble, fince | it can never be fubject to any fuch in- Tae : venience: And the practice thereof will be found | very ealy to any perfon that underftands the fore- direétion parallel to an imaginary line from the centre- SS ee ee a ayy vat j ==> erties A Set ty sy eee Hi Gravel spit field with rhe ~ fmall parcel of Alders ~ gn the middle ‘of it. reduced to the A abe. The bale ad: | meafured - - tne The Bets 1078, cular from ¢ 14064 12306 17580 1819|5124. ‘Area per? & ®_ F: Sect. 4. 9 ae Se 36 Subit) itd. -:-o s12;' 14 Area of amy mass thefieldg «= $3.72 The Alder wood on the weft fide of Gravel- pit field reduced to the A ghz, Ree do8 _ 805 from } - - Bale es ° "2990 47840 4|8|1390 Content - - 2:15 25 aes ia The sfenill ean Alders in the mid Of ° Gravel-pit field reduced to the ay Od eR cae, The bafe d: a 655 Perpendicular fy ‘ 4 : from ¢ - ry Mies ,. 28am 4585 “065. a rn17245° a A. ‘RE Pe Content - + o:2:14 ‘a A a Kiln field reduced to! t t Akilma . The bafe Jaz - - “Bag from & - - har 3650 182500 — q + 812186598 | ee Py 4 : 7 9:0: 23% Wooty Content -— ug Upper Pound Field oto fo. the A | Fe MORE : | _ The bate w x - = 930 Le ied aye c 404 3720 558 on 41311520 oe Aes Rs) P. Content ee BO 26 Be rood Fealaced to meine A DE s, Wihe bale DE.- - 955 roms + - - - - 480 76400 3820 Be a 41518400 P. Content - A; o Beat ins. O7 || ‘Teele Bogey Seid: re= duced to the Sa ey Olan a 4 The Diagon. Fifi THz | of la ce at 680 gu fromz- 300f - Content - Woods houfe and garden reduced to the A ABC, The bafe BC - - 375 Perpend. from A Oi QT 2625 3375 | Aree 1713875 A. Hts P. Content - O:1: 19g Furz-field reduced to the A FGH., The baleGH - 929 SPORE Ee Ne 249 30 5574 2787 2787 ARETE AL a P- Content = 1;2: 19 ] 3 Kaln , , Ons) Kiln ‘wood eahibed: to the ATKL, or as The bafe KI." 14.47 7 Perpendic. from I 450 | 72,050 Zon 71912550 capuige Ahad Mies UE, Content 4 a8) o's 9°: 334 The whole plot reduced to the Trapezium MN OP. Perpendicular ae from N - 1963 Ditto from PB. -.) 9470" Sum - 2733 Diagonal MO ~- 2868 : 21864 16398 21864 5466 7813/8244 Ay Rees Content - 39:90: 30 as on the nght. a” #0 ladies Field oy Ae ~ R ‘baled Wood rie | Ne T be Conte with the dl- ders eee Oy Sinks 3 a ee Kiln Field — pe 9: O 2 Woody Croan Cae es Y Little Bogey al ak ne 9 q Upper Pound Field 2: ° si ee Weeds Houfeand acai Garden - - oO Paha: | Boggy Wood - = "a * Faure Field = 0 > Te02. Kilo Wed = -' 903 We cese Toe Pde ae im oi es 4 ee ving of Shoals and ea by a of the i New Theodolite. Tt AHERE are three methods earn this may fi sCbee: performed ; for the obfervations may be de either on the water or on the land. ‘hofe de on the water are of two kinds, one by the log- | 7 courfe and diftance round the fand ; and then to be plotted as a large wood, or any enclofure taken by the circumferentor. d This method I omit for two reafons ; firft, be- - caule i it is to be deduced from the writers sof naviga- tion; and, fecond ly, becaufe the difances thus mea- P Priced are liable to the errors of currents, which ge- _nerally attend fhoals or fands, that are near to the fhore. © The fecond method, where there are no diftances to be meafured on the water, tho’ flill there is one inconvenience, common alfo to the former, becaufe | © the bearings or obfervations are to be taken on that unftable element, (an-error fcarce mentioned by our practical artifts ) 1 fhall briefly hint at; and {fo ra- ‘ther chufe a third, which is liable to neither of thefe imperfections. Let (in Fig. 30) a boat be manned out witha fie- nal flag, a log and line, lead and line, and to ob- ferve the bearings of any land-mark, a cone fs with _ fights : ‘Take two or more places, as A, B,C, on the -fhore, from whence the boat may be feen on the feveral parts of this fhdal, . I4 One line and compafs (as in plain fail ling) meafuring the ty ry (120 ) Ohya One of the boat’s crew is to found till fe himfelf on. the edge of the fand, by the dept water, and then to come to an ‘anchor ; 3 which be: 4 to fignify to two perfons on the fhore, at B and C, — by his fignal. And then from thofe known bas . marks, B and C, the obfervers are to take the bear- | irfgs of the boat, and to regifter their obfervations 5 which, when done, they are to fignify to the crew — by waving a flag, or by fome other fignal. 4a And in the mean time, to prevent miftakes, lee ya the crew, take the bearings of each of thefe land- sii = : Then weigh anchor, which fuppofe at D. \ Then by founding, proceed to EB, and make like ~ obfervations. And io at E, F, G, &é. till youl have furrounded As fand. 7 And if in’ this procefs, you are about to lofe the 4 feht of oneof your land-marks, fuppofe C, let your © afiftanc at C, who, at that time, will alfo be about | to lofe the fight of the boat by fionals (before-hand agreed on) remove to fome other “objet before-hand | asreed on, fuppofe to H; and then to. proceed ag before. 4 Laftly, ifthe fand runs fo far out to a that the objeé& cannot be feen by the boat, nor the boat by — the obferver on fhore , there may be rockets fired * 7 by t the boat’s crew. and alfo by the obfervers on fhore in the night, whereby thofe bearings may be taken almoft at as great a diftance as the ‘light can be feen. 7 For fuppofing th ey rife but a quarter ofa mile above the apparent horizon, its ftay will be about 9 fe- 7 conds, and its diftance for this quarter of a mile will — be vifible about 44 miles. - ut rockets rife much higher, and then the di- = ftances are much greater, “whereby they are vi- : | fible. / Or two boats may lay at anchor inftead of the : Jand-marks, and then you may work as before. | Now. Babi t = ; ' iG yar ) | Now, fince the land-marks B and C are fixed, ofition may be Jaid down in the draught, as on furveying, by plotting the diftance be- B and C. ‘And then, by plotting the line nd the line DC, according to their pofition, eir common interfection, will give the point D. din like manner EK, F, G, &c. may be plotted ; fo the fhoal: And this froin the bearings taken If this he a ftanding lake, environed by bogs, not _ be walked on 3 che ewvacion: at D, FE, F, £5C, taking their oppolites, may fuffice to plot the fame from the land-marks A, B, C, &c. as well as thofe taken on the land; or, indeed, by the courfe and diftance, as in navigation, if the water be -fmeoth and without a current. ee; fea-fhoals, it is convenient to note at each ob- fervation the depth of the water found by the lead, and the drift and fetting of the current by the log and compafs, while the boat is at an anchor, which may be done with eafe and expedition enough. For while the boat rides at an anchor, her ftern points out the fetting of the current, and the log and glafs will meafure its drift. _ And thefe ought to be noted on the draught, . which may be thus : : The currents may be fhewn, by drawing a dart pointing out its fetting, and its drift by the Roman capital letters, and the depth of water by the {mail figures, All nocturnal obfervations ought to be feveral times repeated. SECT, i ——— =s 7 > — eS = wd tb bas etre ne ey etek piel ett tele ters ety RN SYilew Sa iy, 3 ES SNGe. jutted. | pelt you have a mind to be curious, repeat the ope- : ration ; but when you place the inftrument at C, ‘turn the tube at right angles to the line AB, and there fet it level ; then proceed with the repetition of the work. Only obferve to crofs-level it in this _ adjuftment, and in all future ufes whatfoever. Or the level may be adjufted thus: As before, firft plant the inftrument in the middle between A and B ‘Fig. 32.) and obferve the heights on the fta- tion-{taves, which fuppofe to be as above ; ; and con- fequently their difference, as before, is 3 foot 0.6 inches, Now meafure from C towards the higheft sround A, fome diftance that comes almoft to A’; -fuppofe 4. ‘chains. to D, and DB will be 9 chains, and DA one chain: Then plant the inftrument at D, direct the telefcope to A, and, fetting the bubble to the middle of the divifion, direct your af- fiftant to move the vane, til! the hair cuts the middle of it; and note down the feet, inches, and parts eut by the upper edge of the vane; which fup- pofe to 3 foot 8. 4 inches : : To this add the diffe- rence é : Sr a ba : 2 Son es 3 ss ta Ba, VP Ei oe ion : ae ere ° : Paseo Rem < SECS eae ee ete Ye le hn OS ~ ~ a fa : ie ‘ , 3 3 - ~ av Ty Ee ty ms we a aed tome te os on = _ ~ eee SS — ee —— —_ tsrae > === {Tt a x. = = ———= £ x. > » = * wot oat f ES Oe oe es ee ed x I te x prt ctr ae cee ee by * (¥24 rence 3 foot 0.6 ‘inches, and the fum 6 foot g Soi 4 ches referve. Now direc the telefcope to ite Raff at B, level ep and direct your affiftant to move the vane, till ie hair cuts the middle thereof; and then, if the — upper edge of the vane cuts the foregoing fum6 foot g inches, the hair and bubble are truly adjufted. But — if not, fay, As BD wanting AD, is to the diffe- — rence between the numbers cut by the upper edge of 4 the vane, and thenumber 6 foot g inches; fo isthe diftance AD to a number, which added to that cut by the vane, when lefs than 6 foot 9, and fubtracted from the number cut by the vane, when it is greater than 6 foot 9, will give a number, to which let the affiftant fix the vane; then fo elevate or deprefs the hair or the bubble, till the hair cuts the middle of the vane at B, and the bubble ftands in the middle of the divifions; for then the level will be adjufted. The siya may be again repeated, and at every aoe crofs-levelled, which will confirm the former a adjutt ment. After the inftrument is duly adjufted, you may proceed to ufeit. Let the example be this annexed, (fig. 23.) where A every where reprefents the level, and B the ftation ftaves; and fuppofe the rout be made from a to e; firft plant the inftrument between the ftation ftaves a and b: at A direét the level to aB, bring the bubble to the middle of the divifions, and inftruct your affiftant fo to place the vane, that the hair in the telefcope cuts the middle of the vane ; then in a book divided into two columns, the one intituled Back Sighis, the other Fore Sights, enter the feet, inches, and parts cut by the upper edge of the vane at aB, in the column intituled Back Sights. Then look towards the other fiaff b B, bring the bubble to the middle of the divifions, and ‘direét your affiftant to place the vane'fo, that the hair cuts the middle of the vane 5 then enter the feet, inches, and 4. parts» a BEN, =a he | a) ee ’ omy i” ay J- i i a ¥ BY ah: x ‘on: Vee) A ee a “e eB ¥ . ed iF ay q? a thy Seis 2 : ae + ae ; iat, See, y parts cat by the upper edge of the vane, in the co- | ymn of Fore Sights F | “Now, plant the inftrument at A‘, ftill keeping the ‘Bb exactly in the fame place, and carry the a B forwards to the place cB; now look back > ftaff bB, and enter the numbers cut’ by the vane there, under the title Back Sights ; then look forwards to cB, and enter the obfervation under the title Fore Sights. Do the like when the inftrument is planted at As, A+, &c. always taking care to keep the ftaff in the fame place when you look’d at it for a Fore Sight, till you have alfo taken with it a Back «Sight. Bes rites finifhed your level, add up the column of Back Sights into one fum, and the column of Fore Sights alfo into one {um ; and the difference between thefe fms is the afcent or defcent required. And if the fum of the Fore Sights is greater than the fum of the Back Sights, then e is lower than a; but if the fum of the Fore Sights is lefs than the fum of the Back Sights, eis higher than a: For example-fake, let the numbers be as in the following table. Back Sights. Fore Sights. Feet, nek, Tenths. Feet, — Inch, ‘4 Tenths. SESS of Goan ae Beg Als sky Pee Gist, 318 ee ae Mee i 4220 © 152 Be as a OF ie ts Bi 5/0 2 Fae rari PAE GO! 4 .7 Pie 4520 “ee BBs iE): gry | A AR EN ae 2 1 eye \ Now rs det a Typ ty oo : — ~ -~ ae oe a ng tJ ay eT - . + eran eee Tee = te a ee oat a Sones — x x so Splplytely ess 4 — preies x gy ty r 9 & =a ' 4. = = a <= xe Seen a » oy == trier + ham GM Gad eee et ot wan te OO TE v pees S eet SS EE ee SO a a a Rt en ogee Now follow ine servations well sores notice: oe I. If the fum of the diftances in taking the Backs Sights, is equal to the fum of the diftances in taking © a the Fore Sights, all the minute errors of the inftru- ment will mutually balance and cena each other. a II. And if the diftances thus taken are thora the curvature of the earth may be rejected. For, ifthe ~ diftance from the inftrument be every where about roo yards, all the curvatures in a mile’s gow be lefs than half an inch, rie Til. If the diftances from the infirument to the hindermoft. ftaff, be every where equal to the dif- tance from the inftrument to the correfponding ftaff 5 the curvature of the earth, and the minute errors of : the inftrument will both be deftroyed. | IV. If the diftances of the inftrument from the ftaves, be very unequal and very long, the curva- tures muft be accounted for, and the diftances, in order thereto, muft be meafured, either by pacing, by a chain, or a wheel. V. For the more ready allowing for the curvature, you may obferve, that the curvature for one mile, taken at one obfervation, is extremely near to 8 in- ches, And at all other diftances, itis as the fquare of 1 mile is to 8 inches, fo is the fquare of any other diftance to the allowance for the curvature ; that is, Multiply the fquare of any diftance whofe meafure is taken in miles, by 8, and the produc will give the allow- ance for the earth’s curvature, in inches: This curva- ture is always to be fubtraéted from the numbers taken off the ftation ftaff. Or if the diftance be lefs than a mile, and taken by the four pole chain: Sguare the e “ey a 8, and the quotient eit vs inches parts of of inches to be allowed for the curvature. Sup- 2 the diftance be 30 chains ; then the {quare of me: that i is, 900, when 2 places are cut off, gives 9,00 or 9, which divided by 8, sivey I inch and thoufandth parts of an inch. bee VI. If thefe diftances were taken ibe pacing, ac- Bed ounting 25 to the chain, the curvature may be und thus ; Square the paces, and double it, cut off peg places jo the left-hand, and thofe to the right are the inches of curvature: So, if the paces were goo, then * from 810000 multiplied by 2, that is, 1620000, cut off 6 figures, and you have 1.62, the curvature to be allowed. To fave the trouble of continual calcu- lations you may ufe the following table, wherein the diftances are in chains, and the “allowance i in inches, and xooth parts of an inch, Diftan, Sine aos x T ma = = = . = = meet men ont ~— ~ > ae a =. me 2. = pes — —— = —, pontesses seesenrae naes ae eat — ———— oe ee a — (128) Ditan, Allowance | Dillan. Allowance Chain : SEnehes Pil Chain * a Inches. es 1 10,0012 -l 27 foe. é i Ai 8 0,005 7 28 10,98 3 ot : 29 11,05 4 10,02 Q 390 {5,12 "ane 5 | 0303 at IE a TS 6 | 0,04 | daaliagy' 7 OOD. Me, 3 44535 810,08 - | 34 |tn44 0 9 Be bis | 85 Pee oy tO 810.12 SO sue Ir 10,15 37 1,71 12 |0,18 BS PE BON a. 13 10,21 39 11,91 | 14, 10,24 } 40 2,00 | 15 10,28 | 45 )2528, | | 16 |0,32 | 50 19,12 | 17 | 0,36 55 | 3578 18 |0,40 J pOQ 14450 19 ee | | 65 15.3% 20 | 0,50 70 | 6,12 2T |0,55 | 75 7993 ‘ 22 10,00 Ow hago 23 Be 85 | 9,03 24. 10,72 90 | 10,12 25 ozs 95 [11,28 26 oe | TOO | ¥2,50 VII. Therefore it appears, that a belt method _ to take a level, is to meafure the feveral diftances © t from the inftrument to the back and forward ftation fiaffs ; and enter them in the. field-book, Serine to” | thei ai fas as in the fol- eg , and correct a8 heights from the. be ae toa level | Reh a double dccores ; would advife thofe who ufe the double tele- ae ay {tation to. turn that end of the tele- coward s the fpring, which, before was the cone Gear Forwards, Height | Corrections Diftan. Height | Cor ‘rections Inches | Links - Inches ‘Inches 3:24 | | 418 4,36 4534 6,08 | | 328 at 7917 584) 7.25| 7521 530 ie 959 3261 8,15] 38,14 485 |11,25|11,22 @. 658 10,25 | 10,20 379 | 8,65! 8,63 oehao 0,32) 6,29 | 720 {10,34}10,28 egene te 40,47. | + | 3146 57,85 3146 | 46,47 ‘ie 6 aay 4 : 13%. ey 56 thie the fall in 68 ae is about hts op ci and 3 = of an inch, f kK ‘ey SS OE ary Pa Re TEESE Ee Ea SS gl IS 'S E.Cots oe Of CoLours, T is not worth while to fpeak of the preparation of colours, becaufe they may be had ready pre- pared, at almoft every colour-fhop and fan-painter’s, é§c. Nor to mention but as many as are neceflary and moft fit for the furveyor. I judge thofe to be the beft, which are moft tranfparent. And for portability, I think liquids improper; . therefore would rather chufe thofe colours, which, — before tempered, are dry ; whether in powder, or in - lumps: And fuch as require no other liquid to mix with them (than what is to be had every where) wz. fair water. For Gum Water, with which many colours are mixed, is made by barely fteeping Gum Arabick in Tair water. Carmine, a powder, mixed with Gum Water, is a beautiful red may be fhaded with fome of the fame, mix’d ftronger ; ; or with any reddifh brown, or any fadder red. Carmine is chiefly ufed for drawing of red lines to reprefent the walls of gardens or other places ; and alfo to colour the plans of buildings. Ultramarine, a powder, mixed ate Gum Water, is a moft valuable blue, ft to fhew ponds, lakes, rivers, & “i. at 131 Py, | te rivers, ee it may be fhaded with Indigo Corns | ‘ground with fair water on a white tyle, by the pref- fure of a a knife’ $ point, and then mix’d with Gum re ie | Red alk, a lump, neces called French Chal : ter, and afterwards with Gum Water, {lightly laidon, a is proper t to reprefent roads and pits; and is fhaded by: ae more ftrongly mix’d, geek a. & Sap green, be eepid in water, is of itfelf a good "green to colour trees. be Verdegreece, in lumps, diffolved in vinegar, or in water, makes a greenifh blue, or fea-colour, very ee | Gumbooge, ' in lumps, fteep’d in fair water, pro- “duces a beautiful and tranfparent yellow. | aa cllow berries, fteep’d in fair water, a yellow. Verdegreece diffolved, mixed with Gumbooge, or yellow berries, in different proportions, produces ‘different greens, inclining either to the blue or yel- low, paging to the quantities of either ufed. Indian ink is ufed in drawing the firft lines of a draught, and in fhading of hills and defcending grounds: A proper quantity of it may be liquified when wanted, by putting a few drops of water on a cake, and rubbing i it with the finger until the colour is as deep as defired, But there muft be care taken in the ufing of In- dian ink ; viz. to have three or four different tints of colour prepared, of which the fainteft is to be KS 3 laid , ground by rubbing it on a tyle with fair wa- af ( 132 . | Bs: — Jaid on firft, and fo proceed to the detpett tint ee - not to cover too great a fpace at once; for if the . margins are not fpeedily wafhed off, the ink i vil dry in ftreaks and fpots, and look very ill. a —s Colours are laid on with hale ie ; thofe fit ; for moft ufes, are about the fize of a common writ- ing ae and the length of the hair, without the guill, not to exceed 6 or 7 tenths of an inch: ‘Ing choofing them take fuch only as, when wetted either in your mouth, or in water, will, by ftroaking them — acrofs your finger, form a fine point, and are very® {pringy: And as moft pencils have a hair or two at their point longer than the reft, thefe may be taken off, by cently drawing the point, when the hair is” wet, once thro’ the border of the flame of a candle, In the ufing of thefe pencils, it will be found con-" venient to have them fixed on {mall fticks about 6— inches long, one on each end; whereof one is to be ufed with colour, and the other with fair water, to lighten the margin of the colour, whereby it is in-— 4 fenfibly graduated till it vanifhes into the colour of the paper. . : ‘ All colours are fhaded by others oF the fame fort, but of a ftronger tint: and the manner in’ which they are ufed with the moft facility and fuccefs, is better gained by practice than by precepts. SN ae aii ae Te cS ave Bae ye Z SN AUS Se Mg atsr XI. ee or Fe dal ie Alfo bow to aod for afcents or defcents by finding the borizontal I |B principal difficulty in ufing this Sliding- = Rule, is, in juftly diftinguithing the value of eae ch divifion. And in order to this, it may be ob- erved, that the divifions on this rule, may be di- inou hed into three orders, &c. ie longeft, the Be Beco the Werf And thele different marks di 2 fling uifh their value in a ten-fold proportion, in the — fame manner as the places of a number is diftin- guifhed. : Ge So. that, if the longeft reprefent hundreds, the * mean will reprefent tens, and the fhorteft units. _ And if the longeft reprefent tens, the mean will - reprfent units, and the fhorteft tenth parts. Von Oy AL the longeft reprefent thoufands, the mean a reprefent hundreds, and the fhorteft tens; and in this cafe, the units muft be eftimated by the eye, in judging at divifions, only fuppofed to be drawn, becaule there is not room enough. The longeft divifions are generally numbered by — the figures 1, 2,3, 4, 5, €¥c. and when they are ‘numbered ca 1, 25 3, 45 5: 6, 75 8,93 By 2s 3s MGs 03975 -05:95°1'3 ‘the line: is called a double one. And when the longer divifions are in number only 3 ten, eee ner ms Swe cannot be fo. Nor will they be eafily capable of © rules of greater length; where the multitude of the — alike; one of which moves againft the fixed line a- ~ ( 134 ) 26 ten, and numbered 1, 2, 3, 4, 5, 6, 7, 8, 9, V5 or numbered 5, 6, 7, 8, 9, 10, 20, 30, 4G, 505 00nm broken fo as to begin at any other number, fo as to contain only ten long divifions ; the line is called a fingle one. And thele are called Gunter’ s lines, — Sy the name of their author. Z reprefent equal diftances ; yet, from : ei ‘ an equal number of divifions, in different parts of the rules; either of mean, between the longeft, or . of the thorteft between the mean. P But in order to make this eafy, here follows an % explanation of the divifions laid down on the Foot ~ Sliding-Rule, which may eafily be applied to other © intermediate divifions may be greater. k On the flider are two of thefe double lines, ee * bove, which is alfo exactly like to either of the ~ other ; and the undermoft line on the flider moves © againit a fingle line, beginning with the numbers 5» a 6, ic. and going on to 50. t If the firft 1 be called 2 unit, the following num- bered divifions, till you arrive at the middle 1, will i be units, And the mean divifions will be tenth | : parts. iy If the firft 1 be called ten, the figures 2, 3,4,&c. — immediately following it, will denote 20, 30, 40, €Sc. And the mean divifions, that is, the next longeft in order, will denote units ; the fifth of which is, for — diftinétion, made longer than the reft. And from 10 to 20, between each of thefe mean divifions, the fhorteft denote each two tenth parts; becaufe the diftances between the mean divifions, are divided into five parts; but if the diftances between thefe mean divifions were divided by fhorter lines into ten parts, ? (1 35) parts, which is | feldom done on rules fo fhort, each would : eprefent one tenth part. : a like manner from 20 to 30, that i is, between: the divifions marked 2 and 3, the fame order fol- Jows 3 fave that the diftances between the mean di- vifions (becaufe of their nearnefs to one another) are divided into two parts only ; and confequently each of thefe fhorteft divifions will denote five tenth parts 5 and the eye muft eftimate the other tenths not cut, but fuppofed to be cut between them : tho’ in larger | -inftruments, even here, and elfewhere, the fhorteft -divifions may be as many as thofe between the 10 E ‘ and 20. _ This laft aticide of divifions, ufually continues ‘to 40, 50, or perhaps farther, and are to be read as Pita between 20 and 30. But where the longeft divifions become clofer to- gether, as generally they do, between 80 and go, and between go and 100, which, on the {cale, is denoted by the digits 8, 9, 1, there are but two or- ders of fub-divifions ; the ereateft ftill keeping the fame degree, and the other the next lower decree. And in this one example, the figured divifions de- mote tens, and the other units, But when the firft 1 is called 1003 then the fi- _ gured divifions will be accordingly 200, 300, 400, €¥c. The mean divifions, or thofe the next fhort- eft, will denote tens. The fhorteft between 100 | and 200, where the diftance between the tens is di- vided only into five parts; I fay, the fhorteft here will denote two units each of them ; and the middle between thefe, will denote the fingle units ; which, if there had been divifions, as in large inftruments, would have been denoted by thofe divifions. But from 200 to 300, from 300 to 400, and from 400 to 500, the diftances of the divifions reprefent- ‘ing tens, are divided only into two parts, and con- fequently, each of thefe fhorteft divifions muft re- K 4 prefent ( 136.) prefent five units; and all other units, cithel more — or lefs than five, aut be eftimated by the eye, by q fuppofing each of thefe diftances cut into five parts, WNeverthelefs, in larger inftruments, thefe divifions may: be cut and eftimated as before ec. Towards the latter end of the line, the divifione i en thefe fhort lines are fo near together, that they {carce admit of three orders of divifions, and con- — fequently (fuppoting the longer divifions to denote hundreds, as in this example) ) the units mutt be efti- mated by the eye. And in like manner, if the longer or Genned di 4 vifions denote thoufands, the ines ‘of leffer length will denote hundreds, the next inferior, tens, €8c. But becaufe, by infpection, on this rule it will appear, that more than three places cannot be di- ftinctly eftimated; and, that thofe are iufficiently 4 exact for all the ufes it is defioned for; a farther die : : 2 ; vifion, and confideration thereon, are omitted. If the firtt i, that is, the beginning of the firft — line, denotes a unit; then the middle 1, or begin« ning of the fecond line, denotes 10, and the laft 1 denotes 100, So, if the firft 1 denotes 10 ; the fecond 1 denotes roo, and the laft 1000. In like manner, if the firft 1 denotes 1003; the fecond denotes 1000, and the laft 10000. And fince, when the value of the firft 1 of any line is known, the value of the other figures and divifions are known alfo ; therefore the Jatter line is to be read by the former directions, And thus are thefe three double lines to be read, as has been fhewn, for the former. But the fingle broken line, which is on the fixed art of the Jeg of the rule, is not to be confidered in this arbitrary manner. For the longer divifions have affixed to them their values, which ought to be confidered as unvariable, unlefs \G aoe, : Pi eat Se ee via: ss ’ . fo tisiaey ne one . is caine, oo 7” a = ce es ; Sy RA SRS ge te ae See 07) Pat 10, the diftances of the longer Ainere which are numbered 5, 6, 7, 8, 9, 10, are divided into 10 parts, by mean divifions ; ; and therefore, fe mean divifions denote tenth parts. And thefe each denoting therefore half of one tenth. | ae a From to to the end of the rule, the diftances be- tween the longer divifions, are each divided into 10 3 parts ; and therefore each denotes units. And the 4 - diftances between the units are each divided into 4 & parts 5 ; therefore each denotes one fourth part of an Pmanit. °4 In the double lines, let the diftance between the 1 at the beginning, and the 1 in the middle, be _ called the firft fcale ; and the diftance between that * in the middle, and the 10 at the end, be called the fecond fcale. The uppermoit of thefe double lines is marked with the letter A, the next with B, the | third with C; and the tnidermniont: which is alfo called the girth-line, with D. | On the lines A anal B, in the fecond fcale, there are placed the {mall figures **, denoting an index — fixed, tho’ the value of the divifions fhould vary. Prd. on the girth-line, again{t 12, is generally a hand or index for the like ule, ~The two upper lines are generally ufed for cafting up the furfaces of planks, - The two under ones for finding the folidity of timber. ~ Having thus far defcribed and explained the read- ing of this rule; I fhall proceed to fhew its ufe in -meafuring planks and timber, But fhall firft fhew the cuftoms ufed in taking their dimenfions, And © ules ig ea neceflities hereafter to be - = ee eee oe E15 ea 1 divifions are each fubdivided by one fhort line, - = eed (138 ) And fief for planks ; the buyer hath the liberty of meafuring the dimenGone on that fide of the plank he judges moft advantageous to himfelf. _ Then the length is meafured either with two two- feet rules, or two-feet rules, and five or ten-feet rods. The length is meafured in feet and half feet, andy in fome places, to quarters of feet. Then lay half this length from the upper part, down towards the butt-end ; where, with a piece of chalk, make a mark, At that mark, or nearer the butt-end, if the buyer think it to his advantage, is taken the breadth, in inches and half inches. If one fide be wainy, the breadth is taken to the middle of the wain. If both fides are wainy, one wain is imeatiieeele the other rejected ; and either of them as the buyer thinks fit. Having thus got the length and breadth ; call the firft long divifion on A, and alfo on B, each an u- nit, ‘Then fet the index on B, againft the breadth in inches on A, and againft the length in feet on B, will ftand the content in feet on A. EX AO McP loa Let there be a plank, whofe length 1s 24 feet and a half, and breadth 17 inches and a half; I demand the content ? Set the index (or 12, in the fecond fcale} on B; againft 17 inches and a half on A, and then againft 24 feet and a half on B, ftands 35 and 3 nearly on A; which is the meafure of the plank required. But when the feet, in length, on B falls beyond the end of the line A, then call the firft 1 on A, a ten, and work as before fhewn. at 4, . be 45. feet and a half long a and 39 road, what 1s the content § ? - the index (or 12) on B, againtt 39 on A, ad and a half on B, will fall. beyond the upper end BE os a ‘Therefore fet the index on B, againft 39 on A, will and. a on A, the content required, _ Thefe are all the varieties which happen in plank ‘meafure. But notice may be taken, that from this content | mutt be fubtracted as much meafure as will ballance all the vifible faults: and this is generally left to the judgment of the two meafurers, and generally done before the contents are entered in the accounts, or indeed, before you pafs to another plank. “There are fome differences in the cuftoms of dif- ferent countries, tho’, for the moft part, the fore- going are the molt generally ufed. _ The Htias generally ufed in taking the dimen- fions of timber, are not much different from thofe ufed for plank. For the whole length is firft taken in feet and halves, then the middle is found and chalked, where, _ Or nearer the butt-end, according as it is the buyer’s advantage, the ftick is girthed with a {mall line, which is exactly quartered by twice folding; this quarter is meafured in inches, halves, and quarters. find if the tree’s bark is not peeled, as always hap- pens in ftanding timber; then from the foregoing girth muit be made an allowance for the bark, which is ( 140.) oe is ufually thus: for trees girthing one foot, allow one inch, and fo proportionally for all others. But for beech, elm; afh, and fuch as are thin barked, the allowance muft be a {mall matter lefs, er. It is alfo to be obferved, that, a ftick is not called timber farther than it will hold half a foot girth. Alfo, that if there be any confiderable arms which | hold half a foot girth, they are alfo called timber, and meafured as fuch. CASES Having thus taken the length in feet, &¢. and quarter girths in inches, &¥c. fet 12 (the index) on _ the girth line, to the length on C, and then againft the girth on the girth line, is the folid content on C. ees : EX A Mee ee 2h Let a tree be 24 foot and a half long, and its. quarter girth 17 inches and one fourth ; to find the. folid content : Set 24 and a half on C, againft the index on D, the girth line; and then againft 17 and one fourth on the girth line, ftands 50 three fourths on C, the folid content of the ftick. € Ashe When, by the foregoing directions, An rule is fet, and the girth on the girth line is beyond the upper end of C; call the firlt 1 on C 10; and then work as before, E X- at ree be 20 Hate iy pa dos ost and 4 a tO Bn the ae TA ee ng io [aN When the girths on D fall fhort of the lower end of ion ‘call the middle one on C, aunit; and then, ae allt the figured divifions, below the middle 1, will ee be tenth parts of feet ; then worl as above. i 3 7] | yet i = X A M PLE mL CASE Hil. Vee fick be 3 foot tones and 6 fore oirth 5 to find the folid content; ~~ WAcéountings the middle 1onC an unit, fet 3 on’ __-C,, againft the index on D; and then, again{ft 6 on ae D, ftand 7 ‘tenths and a half onC; Bie fcligiry’ re- quired, | ' kes Py EXA é PLE Iv. - Tes a ftick be feven Foot and a half long, and Pa four inches ; ; to find the folidity : | Set the index (12) on D ant 7 and a half in » the fecond icale on BE; then againft 4 on D ftand 2 7 8 tenths i) ( 142 ) j tenths and a third on C: fo that the folidivy 4 ay * part in ro of one foot. N. B. T ho’ ae i not what ts called timber, yet fince alders and other fhrubs, ufed by turners and. others, are often meafured, be they never fo {mall ; I thought it proper to infert fome examples of this kind. | In the three foregoing cafes, the girths of the fticks fell on the girth line C, without any arbitrary alteration of the values affixed to the divifions ; which fixed values are abundantly fufficient for com- puting the folidity of moft fticks ufually to be met with, if the fingle line C be advantageoufly broken. For, if a perfon defigns his rule for the meafure of timber only, that is, fuch as never girths lefs than fix inches ; then the girth line beginning at fix, will — run to fixty inches: above which, few fticks will — out-run, But if he defiens to meafure alders, fhrubs and fmall things, €&c. often meafured by turners, wheelwrights, and other artificers, ufing this fmall fluff, the beft way is to have the line C broke, and to begin at 1 and a half, or 2, and end at 15 or 20, according to the fize of the ftuff they moft deal in. But that the line, as ufual or occafionally broken, may ferve for the computing of common timber, timber extraordinary large, out-running the girth line, and alfo for fhrubs and fmall twigs; it may not be amils to confider the following direétions and examples. And in the firft place, we will enquire into the ufe of the rule in computing the folidity of fuch large fticks, as out-run the affixed values. of the di- vifions on the girth line. For which obferve, that the length of a ftick al- ways to be found on the upper end of the line C, 4s to be fet to the index; the divifions on the girth line Eb be aah, Ny | Tine numbered 6, 7, 8, &Fc. are to be accounted 60, 70, 80, &e. and that, in eftimating the folidity of the ftick, the divifions on C are to rie eftimated by 100 times the value arbitrarily taken thereon by the length : : that is, if the fecond fcale of C be called units in the length; then, in the folidity, the fame ‘upp per part fhall be called hundreds, and the lower : Ween tens in the length; then, in the folidity, Bs upper part fhall be called thoufands, and the lower part hundreds, | a EXAMPLE V. ba Let there be a flick, whofe length is twenty-five feet, and girth forty- fix inches ; and let forty-fix be above the upper end of the girth line: to find the folidity. Then fet twenty-five in the fecond feale of C, a- eainft the index on D; and then againft (4 and 6 tenths on D, which in this cafe reprefents) 4.6 inches the girth, ftands 367 foot on the firft fcale of C; eftimated according to the preceding directions, EXAMPLE VI. Let there be a ftick, whofe length is four feet, and girth forty-fix inches ; and let forty-fix be above ie upper end of the girth line: to find the foli- ity. Set 4 in the fecond fcale of C, againft the index on D; and then againft the girth 46, on the lower part of D (which, ; in this cafe, will be reprefented by the affixed value, 4 and 6 tenths) ftands 59 feré on the lower part of C, eftimated according to the preceding directions, For 3 (144 ) For very {mall fticks, whofe girth falls below chs. ‘ ; beginning of the girth line D; obferve, that the — length of the ftick always to be found on the firft feale of the line C, is to be fet to the index; the : ' divifioris on the girth line numbered 10, 20, 30, 9c. are to be accounted only 1, 2, 3,€8c. And that efti- 4 mating the folidity of the ftick, the divifions onC are to be eftimated by the rooth part of the value arbitrarily taken thereon by the length; that is, if the firft fcale of C be called units in the length, then in the folidity, the fame lower part fhall be called hundredth parts only; and the upper end tenth parts. But if the lower end of C be called tens in the length, then, in the folidity, fhall the fame lower — part be called tenth parts, and the upper end units, — EX AM?P.E fev Let a ftick be fifteen feet long, and let its girth be three inches; and let three be below the lower part of the girth line: to find the folidity. | Set 15 feet, taken in the firtt fcale of C,.to: the index on D 5 and then againft 3 (which, in this cafe, will be reprefented by 30) in the upper part of D, ftands the folidity 9 tenths of a foot, and a quarter of another tenth, EXAMPLE VII. Let a ftick be three foot long, and Jet its girth be two inches ; and let-two be below the lower part of the girth line: to find the folidity, Set 3 foot, taken in the firft fcale or lower end of C, to the index on D; and then againft 2 (which, in this cafe, will be reprefented by 20) in the upper part — an re : 4 places where the cuftom alti the taking. tuto! minute “athe of ‘a fasts or when» the i (145 > part of D; lands the’ folidity, eight hundredth parts of a { foot, and'fomething more. . wanes ;-the cuftom is to take the length, and find | | amide: in the fame manner, and with the fame allowances as were obferved in round timber; and ‘then, ‘in this middle, either with a pair of callipers, ‘or the edges of two rules applied to. the flat faces, to take the breadth and depth of the ftick.. Then, to add the breadth and depth together, and to ufe half their fum, as you: before did the quarter girth ‘of around’ ftick, | , ths at: mY Himes vin EX A MPLE, ee Bick be twenty- ee foot long, fourteen inches broad, and twelve deep : to find ‘the Bo em ha to this i method. Becaufe 14 and 12 vive 26, whofe half is 13, fet 25 on C againft the index on D; and then againft | ‘13 on D, ‘ftands almoft 29 foot and a half folid. And tho’ this cuftom makes the ftick fomething more than in fact it is, by adding the breadth and depth together, and taking their half for a girth; yet, in a whole tree, only. hewn to a fquare, the difference is fo very fmall, that the cuftom may be admitted, For in this example it may appear by the pen, that the folidity thus is 29 42, foot; and the true folidity, if the ftick be allof the fame bignefs, and a : without “Oe as" Bia for Gedien slither 5 mrtaret cathe iiaher 4s hewn to that form: which is ufually “called fquare,’ ‘tho? att 1¢ fame time there is moft commonly four ( 146 ) without wanes, will be 29 24,, differing from ses 3 former only .32,, or % of a foot folid. Neverthelefs, in fticks whofe breadth differs e ; much from the depth ; the error is intolerable, and 7 ought not to be admitted. For, lec there be a flick 26 foot Leia 20 — broad, and 6 inches deep; then, by the cuftomary way of adding, the width and doptt together, the fo- lidity will, as before, be 29 442, foot; but the true — eh will be only 20 442: and fo the error is 8 23. foot, almoft a third part of the ftick. For the ready management of fuch timbers, there may be placed on the other leg of the rule, another flider ; having the fliding part and the upper fixed _ line, exactly the fame as in the former leg; but on the other fixed part, a double line of the fame ra- dius with the former, but broken and inverted. And as the lines on the former leg were diftincuifhed by the letters A, B, C, D, fo the lines on the latter are noted by che betes E, F,G,H. And as the divi- fions on the lines A, B, C, were intirely arbitrary, fo the lines FE, F, G, are alfo intirely arbitrary. And on the line H, which is inverted, and beginning at 1 and a half, and running on to 140, the values annexed to the divifions, may be varied, or remain unvaried. But on the line E being direét, begin- ning at 1, and running on to soo, the values an- nexed to the divifions, may be conftant. The line H, I call the depth line; the line G the _ breadth line; the line E, I call the length line, and ¥ the content line. The ufe is fo fhort and fo eafy, that, in a few words, and two or three examples, it will be plain. For, fet the breadth on G, againft the depth on ° H, and then the length on E will ftand againft the folid content on F, Let . ee | | TB | (147) = | | Lethe fick ‘be that of the laft example ; where ob 19tl was” a5 foot, breadth 20 inches, and aS gael we 3B iit Feliebhedch 20 on G, againft 6 on H; and ee againft 25 on E, will ftand on F almoft 21, e folidity required. | Bere ‘to avoid confufion, remember, that what- foever is is the value of the divifions on G, the fame fhall be the value of the divifions on F. That is, if the f rmer divifion on G be units, and the latter tens, then the former divifion on F fhall. be units, and the latter tens. And if the former divifions on G be tens, and fo the latter hundreds ; then the for- mer on F fhall be tens, and the latter hundreds. Tf the length on E falls beyond F, call the for- mer divifions on F, tens, and the latter hundreds. TF thé length on D falls fhort of F, call the for- mer divifions on E tenth parts, and che latter units, UE EXAMPLE. pg ey eg pee gine gene ey _ Let a ftick hewn to unequal fquare fides, have its length 46 foot, its breadth 30 inches, and its depth 20 inches; then, when 30 on G is fet agpainft 20 on H, £6 on E will fall beyond the line F'; there- fore call the former divifion on F, tens ; and then fet as before, and againft 46 on EF, will ftand 191 4 fait on F, which is the folid content, Ki The fhell, or flitch of timber, is readily caft up by this rule ; for, take the breadth on the flat fide in the middle, and one half the depth in the mid- die, and work with the length and thefe, as tho’ it were a fquare ftick, and you have the folidity fuf- ficiently near. ___It is indeed true, that this is lefs than the true folidity ; but in regard of its value it is thoughe pouet. : L. 2 ite nee =a -E-G_R- ELA ER LEO RAL LET EASE Sad LL BE LL RO RURUETA DESL ODES aha bekhatel EOL LE EULER OL Rat etrbatalk kt ch kit 1 27 ttetebate abet clk tt hee -L the needle will point out. the bearing of that front : to this add or fubtraét 90 degrees, you. will have. the directing number ; that is, the bearing of the. line perpendicular to the front. Now plant your inftrument at the place, whence the original building is to be viewed. Bring the in- dex to “the beginning of the divifions, and turn the whole inftrument about, till che needle points at the directing number; and then fcrew it faft. Bring the telefcope to the beginning divifions in the verti- cal arch, and level the “whole inftrument : fo will the inftrument be duly feated and re@tified for obferva- tion. In order to get eafily a due knowledge of per- fpective in general, and particularly of the ufe of this infrument in drawing, turn to the figures in Plate V, and raife up the draught PK (Fig. 1.) per- pendicular ARS 8) pendicular to the plane of the leaf upon the line . W K, and life up the plane AY W (Fig. 2.) till it is per rpendicular to both the plan of the leaf, and alfo to the draught PK; then raife the draught ABW (Fig. 3.) till it coincides ‘with AY W, and confequently will be perpendicular to the plane ofthe ~ leaf, and alfo to the draught PK; fo will the two. draughts. AW, PK, be the two Grants of the mo- dule, reprefented to the eye.” Lift up the draught: aV (Fig. 4.) till it is: perpendicular to: the plane. of | the leaf, and it will be the picture defigned to be drawn ; and will coincide with PK, thé font of the module. “I is the point on the sround whence the ‘building is to be feen. Lift up ET, till the point Eis perpendicularly over the point T: And Eis the eye of the f{pectaror, or the centre of the telefcope. Now if you conceive ftrait lines drawn from the eye at FE, to the feveral points A, B,C, D, €sc, in the module, they will meet the picture in the points a, b, c,d, %¢.. which are therefore the true appearances of thofe original pa A,B,C, D, and a line drawn from a to b, will be the true ap- pearance of AB; and fo of all-other lines: for the rays of light come to the eye from the picture in the very felf-lame direction that they would have come from the original module, Thus much by way of introduction, Now, in order to draw the picture: Affign on your drawing board any point C, at pleafure, for the centre of the picture’; and ee CV. the hori- zontal line, and perpendicular to it, the vertical line CX; from thefe two lines, all the parts of the build- ing are to be laid down by their apparent diftances from them, | N.B. By ie centre of the sistas I mean that point, whence, a line drawn to the eye is perpendicular Yo , ( 154 ) to the plane of the picture. The horizontal line is that which paffes thro’ the centre, and is parallel to the bo- vizon 3 and therefore is the common interfection of ibe pifture, with the plane of the ocular horizon. The principal line in thefe draughts is, that coin, or that angle which is common to both the picture and the module 5 and confequently every where pro- portional to the building it felf: and is the firft Jine to be laid down and divided ; which may be done thus: Let the example be as in the preceding {cheme. Direét the telefcope tothe point P in ‘the build- ing, and you will find the index on the horizontal plate of the inftrument cut 32 foot and a half, and on the vertical arch 2 5 foot; lay the latter above the horizontal line CV, perpendicular to it, from | C to X; and the former from C to x. Then, by help of the fquare, draw x P, X P perpendicular to CV, CS, wheace the abeage appearance of the’ point P is found. In like manner may be found the perfpective ap- pearance of any point whatfoever, whether it be co- incident to both the module and picture or not. _ Deprefs the telefcope to W, in the building, and (in this example) it will cut on the vertical arch g foot ; which, becaufe you look downwards, lay from x downwards to W in the picture, and fo you have the true appearance of W. And confequent- He if you draw P W in the picture, you have the rue appearance of the line P W in the building, If you elevate the telefcope to A’, in the build- ing, it will cut on the vertical arch 15 foot; which laid from x to A‘ in the picture upwards, ‘becaufe the point is above the horizontal line CV, will give the reprefentative of that point in the picture. And thus may every one of the points B’, O', D’, &e. be laid down in the picture. Direct RFP: ( 155) ¢ ‘Direé the telefcope to K’ in the building, and you will find on the horizontal arch, that the index cuts 69 foot and a half; which laid from C to L’, gives in the picture, the reprefentation of the point L’. : Thro’? L’, draw FE’ L’K’ perpendicular to CV, and A’E’, BF, C’G’, ce. parallel to it, thro’ the | points A’B’C’, &c. and fo the coins EK, and the ‘tops and bottoms of the doors and windows may be limited in refpect of their heights. | Direct the telefcope to Q, and it will cut on the . horizontal arch 38 foot anda half; which lay from C to Q’, and it will determine the appearance of Q’, Jn like manner may N’; and the jaumbs of the win- dows Q.N, M O’, be laid down. As alfo the other windows, doors, €3c. For the returned front aW, draw PC, WC, AC, BC, CC, DC, &e. and they will limit the heights of the parapets, facia’s, windows, €&c. Direc the telefcope to b, d, f, h, &c. and it will cut on the horizontal plate 16 foot, 17 foot and a half, 19 foot and one third, &c.----, which laid from the vertical line XS, will give the breadths, reprefenting the piers and windows. The fame may be done for the chimneys and their returns ; or for any other lines, breaks, &@c. And io the feveral parts of the perfpective appearance of a building may be drawn without meafuring. That this compendium of perfpective may be compleat,- it may not be amifs to lay down the ne- ceflary Theorems in the moft general manner poffible ; and herein I fhall ufe thofe terms which Dr. Brook Taylor hath thought fit to mention, they being more comprehenfive than fuch as are ufed by the other writers on this fubject. ty x _— —- cS sae Tetpiyt Tyr > ? a ae - = Theor. 1. All the lines of any object (as in a mo- dule or building) which are parallel to one another, and (956) and to the pidture ; will be hepactenton by parallel ’ on the picture. Theor. VW. All bate parallel in Mahe oll ies or building, which are perpendicular to the picture, will, if continued, run to the centre of the picture. Tho? thefe parallels be or be not ali in the fame. plane. Theor. I. All lines in the module or building, perpendicular to the plane of the horizon, will be in the picture, perpendicular to the horizontal line. And thefe three Theorems are fufficiently allie: in the preceding example. , Theor. IV. All lines in the modale or oom parallel to one another, and to the plane of the ho- rizon, but oblique to the picture (as in the follow- ing cxample, fee Plate VI.) will meet in fome one point in the horizontal line CV. Thus the paral- le] lines in the front Wa, meet in the point V-3 and thofe of the front PQ, meet in the point Y. Thefe points V and Y are (by Dr. Zaylor) called the vanifhing points of thefe parallels, and vy him are ‘thus found : From T, the point reprefenting the place from - whence the building is to be viewed, draw a line pa- rallel to thofe parallel lines in any front or face. of the object ; and where it meets the ground-line SR, draw a line RY perpendicular toS -R, and its inter- fection Y with the horizontal line V Y, will.be the vanifhing point required. ® Theor. V. All the lines of an. objeét which are parallel to one another, but oblique to the picture, and not parallel to the plane of the horizon, will be reprefented by lines meeting in a vanifhing point, found by the interfection of the picture, and a line 4. drawn o 4 157.) | j drawn from the eye parallel to thofe parallel. lines. But this vanifhing point will not be in the horizon- | tal line, but either above it or. below it. Theor. VI The fhadows of all parallel lines oe oa by the interfetion of the fun’s rays, will, on the ground, be. parallel; and confequently in ‘the pic- ture, either be parallel, as in Theorem I. or elfe meet ata point in the ana) line, as in T. heorem Il, ue ¥ pa% aaikter,. as in the former example, the centre of the _ picture being determined, the parailels which were perpendicular to it, and alfo parallel to the plane of the horizon, were, by the help thereof, eafily drawn ; fo in this example following, fince the vanifhing - points are of no lefs ufe to draw all parallels, I fhall, _for this purpofe, thew one general rule, without any exceptions; not in the geometrical manner {hewn by Dr. Taylor, but by the help of the new Theodolite, as now improvea by Tuo. Hearn, mathematical inftrument maker, at the Hercules and Globe, near Eixeter-Exchange in the Strand. | Let the example be that contained in Plate VI. where, as before, .raife the draughts PQ, AYW, ~- ABW, (AW Y coinciding with A W B,) Fig. 1, ay 3. and you have the module reprefented to the eye; raife the drawing a Q perpendicular to the plane of the- leaf Fig. 4; and it is the :plane of the picture defigned to be drawn ; but it is oblique to each front of the module:.and the coin or ner PW is the only part of the ee or building which coincides with the picture. Raife up TE (Fig. 5.) as in the former example : ae E repre- fents the eye beholding the building or picture. Plant the inftrument and a ftaff in the line S W, which is the ground-line of the picture, or elle at : equal diftances from it, that is, parallel to it. And | | find, (158 ) find, as in the foregoing example, the dieing, number. Plant the inftrument at your defigned avitit Ts and rectify it as in the preceding example. Affume the centre C, on the drawing board, draw cv, CX, as before. Then lay down PW, and its feveral divifions- — A’, B, &c, and the two points a, b, as in the for- 4 mer example. Draw Pa, and Wb, and produce them till they meet: fo fhall their interfection V be the vanifhing point fought. . Ufe this point V as you did the centre of the _ picture in the preceding example ; and then goon to draw the front aW as before. In like manner find the vanifhing i as wid proceed to draw the front P As to the pofition of the picture, fome peHious will have it parallel to a front, others parallel to the diagonal of the plane ; others chufe rather that po- fition to which a line drawn from the eye to the common coin PW may be perpendicular to the plane of the picture. And in this latter, there is no occafion for the di- recting number, or the bearing of any front: for take T the ftation at pleafure ; bring the index to the beginning of the degrees on the horizontal plate, and turn the whole inftrument about till you fee thro’ the telefcope the coin P'W, there fcrew it faft, and level it; and proceed in all refpects as in the laft example. ( 159 3 a: SECT. XIV. ‘Ter pai tsin and ufe of the Perambulator, or mea- furinge wheel. PP AAIS inftrument, as it is now made, confifts of Ger, a light wooden wheel fhod with a thin iron ring, the outfide circumference whereof is 99 inches, or half a ftatute poles a frame of wood of about three feet long, including the handle and the two _ cheeks, between which the wheel moves ; alfo a box of about 10 inches diameter, containing a motion | work ; on the face whereof are three circles, and their _ indexes or hands; a revolution in the fmalleft circle -anfwers to the length of one gunter’s chain, a revo- lution in the greateft circle anfwers to one mile, and a revolution in the other circle anf{wers to 50 miles. The circle of one chain is divided into 100 equal parts, fhewing the links; that of one mile is divided into 320 equal parts, fhewing the poles; and the other circle is divided into 50 equal parts, fhewing the miles: So that the meafure of any diftance, run over by the wheel, will be expreffed in miles, poles, and links. The motion of thefe indices is produced by the ro- tation of the wheel,-whofe axis, as it revolves, com- municates motion to the work in the box through a groove or channel cut in one of the cheeks, The length of the initrament, from the extremity of the wheel to the handle, is about four feet and a half ; and its weicht is about twenty-three pounds, the wood work being of mahogany, and the mo- 4 tion 4 160 ) 4 tion work of brafs: Buti it may be made much fhorter 4 and lighter. te in vk eater To ufe the perambulator in the meafuring of diftances. Being well afcertained of the accuracy of each pait of the inftrument, open the lid of the box, fet all the hands to the mark o, or beginning of their refpective circles, and fhut the box; then tak- ing the handle in both hands, drive the wheel before you, directing it towards fome fixed point; when the propofed diftance is run over, obferve the pofi- tion of each hand, and thefe being rightly eftimated, will give the meafure’ of that diftance,, reckoning: al- ways from the point on which the wheel refts, at the beginning and end, or the point perpposiicularty: un- der the axle, | ail5 To find che diftance run over; obférve, firft, the ‘mile index ; fecondly, the pole index ; ‘and, thirdly, the link index: If the mile index has not moved’ one divifion, the diftance is lefs than a mile ; then the pole index will fhew the whole poles,» and the link index fhews the links above the even poles: But, if the mile index has moved one or more divifions, the diftance run will be fo many miles, and the -over- plus poles and links will be fhewed ewer theis « eed ‘tive indices. Example %. Suppok the mile index ftands sha: tween the beginning of is divifions and the firft mark ; the pole index at 221 ; andthe link index ato; "then the diftance run over will be 224 poles, or §5-chaing and 25 links, or 5 furlongs and 2x poles. Example XI. Suppofe the mile index ftands be- tween the gd and 4th divifion; the'pole index be- tween the 184th and 185th divifiens ; and the dink index ; ( 161 ) inde at its 67th divin’) then the diftance run ove r will be 3 miles, 184 poles, and 17 links ; the ther 50 links being equal to 2 a are accounted for in‘ a the pole circle. ! When you have feveral fircceffive lines to mea- _fure, or one great diftance, in the rout of which the ermediate diftances of feveral places are to be noted ; the three indexes may be fet at the begin- ning of their refpect circles, at the commencing each new line or diftance 5 or, “which i8 the better way, do not fet the indices anew, but let them continue to revolve, and note at each diftance the numbers — fhewn by the indices; and thus the whole diftance pafied over in any given time will be at once thewn 3 then the intermediate diftances, which were mined. will be found, by fubtracting the aha entered in the field. book from-one another. To this inftrument may be annexed two iron rods, which may lie clofe under the cheeks, and when wanted may be let down and ferve as legs, like thofe : “of a wheel-barrow : Allo to the cheeks may be fixed two ftandards, which reaching above the wheel may : fupport a crofs piece, whereon a Theodelite, or other furveying inftrument may be fixed, whofe centre ftanding over the axle-tree, will always cor- refpond to the place where the line begins, and, con- _ dequently, the trouble of fetting the head of the three legged ftaff over the (ation-ftaff hole, will be avoided; befide which, a furveyor ufing fuch an in- _ ftrument, will be benefited’ in the following’ par- | ‘ticulars, | | ee The tirefome re pckbion of ftooping with the chain or pole, will be avoided. M In ( 162 ' : In the trouble of handling the arrows, chee ace count, and the difficulty of flicking them into — hard gravelly or rocky ground, or into the ground s ‘when frozen. , The expence of one, or both chain-men will be faved. § ‘There can arife no fuch errors as frequently hap- pen to the chain, fuch as its {waying, yawing, the difference of pricking down the arrows, or the di- verfity in the lengths of chains. The length of a days journey may be meafured without keeping any account, till the end. In taking the angles of elevation or defcent, the Theodelite always ftands at the fame height from the ground, } A. furveyor with one or two affiftants, and this — inftrument, can meafure any quantity of land in a~ bout half the time he could do it in by any other means. To the ufe of this inftrument it may be okiected, that in going over many plough ridges, or ant-hills, there will be a confiderable difference in the lengths- given by the chain and wheel; there will, indeed, Be fone difference, and athe more than will hap- pen in meafuring the fame diftance forwards and backwards by the chain; for, by a trial on a com- mon full of large ant-hills, in the moft uneven part thereof, the wheel gave a pole more than the chain, in the length of a quarter of a mile, and going over more than roo hills; and in meafuring this length back again, the wheel gave the fame di- ftance ; but the chain gaye near half a pole more i , than ate | oe a than before: Befides, an experienced artift would avoid taking the worft place. Ei paffing of rivers, ponds, woods, brakes, &¢.. they are of fmall import; for a perfon of any fhare of fagacity, will readily know how to proceed on fuch _ €mergencies. sates, €fc, and without varying the indices ; thefe _ contrivance to do this being provided, the indices are fixed ; and the weight. of the whole, though “increafed by the Theodelite, will not much exceed and may be fo contrived, both frame arid wheel, as to take to pieces for the convenience of carriage, and packed up in the fpace of little more than a cubic foot, ; M 2 OS Reo ith regard to the objections concetning the By With regard to the paffing of hedges, ditches, are eafily anfwered; for by hafping the wheel, a © ene ene ae ese ee FES = thirty pounds: But they may be made much lighter; Fe i ag a on we on ne aie Be oe ee x _ So 9 ot Ee nn we ae oe we oe ee SS — x, — fect - ieee: the pe T has been fuppofed, that a needle, playing free ‘ly, which has had a ftrong touch from the load- {tone, points exactly north and fouth. But by num- berlefs experiments it has been proved, That the needle does not point exaétly north and fouth, any where but in fuch places on the earth as lie on one particular line, which is therefore called, The Line of no Variation; and this line is found to change its fi-’ tuation by a flow motion, from eaft to weft. ley now pafies from the weftward of the Cape of Goody Hope to the Weft-Indies. And the variation of they needle in all other places is known conftantly to alter) by a flow change. In England that end of the needle™ which has been fuppofed to point full north, de- viates from it now about 14 * degrees to the ‘welt- | ward ; and is ftill, and alfo will for many years con-— tinue to increafe, even till it arrive at its Maximum 3” | and then will decreafe till it vanifhes, and then” change to the eaftward, as it formerly, was; and by : ano fcillatory change will fo continue to alter, | This variation of the needle'would no ways hin-)) der the exactnefs of the furvey, if it was conftant ; nor is the alteration of the variation capable of cate | * “Inthe year 1749, the deviation to the weftward was about i7 degrees. . i * o ee) (1 és) ns pace of ti time not exceeding four or five years. it if the quantity of the variation be not known, | and confequently not allowed for, the north point of the compals, which the furveyor draws on his map, convenient i in all places to find it; and this may be | eee ways: But by none more readily, more | cafily, or more exactly, than by the univerfa! dial, as now made by Mr. Hearn, the inftrument- _ maker mentioned before, the figure whereof is in the | plate fronting the title. | _ This dial confifts of four principal parts, viz. the Foot or Pedeftal, the Meridian, the Equinoffial, and | the Bridge. The Pedefial contains a box and a ne edle, and _ three {crews in the foot, it may be placed truly hori- _ zontal; and while the ‘pedettal remains in this firu- ‘ation, the box and the circles of the inftrument may | be turned: round to acquire a proper pofition of the | ‘meridian. ‘The circumference of the box is divided’ | Into 360 degrees, and within this is another circle. divided into four quadrants, and each numbered with go degrees. On the plane of that part of the pedeftal which is moveable are fegments of circles, | a any fenfible error in a furvey that is performed _ | will err as much as that variation is. It is therefore. two crofs levels; whereby, with the help of the | 7 containing a table of the equation of time; fhewing | the months, and days of the month, together with the minutes which watches, or equal time-keepers, are too faft or too flow for the motion of the fun: And on the outer margin of this moveable part, is a circle divided and numbered, either into 360 de- grees, or into four quadrants, containing go degrees , each ; beginning with o degrees, at two points dia- | metrically oppofite: This circle flides againft the fixed ring of the cote on which is a Vernier’s icale, (commonly called Nonius’s) for obtaining parts of degrees. M 3 The C60: 5° eg The two {crolls which ftand upright on the cham of the pedeftal, and fupport the rings of the inftru- ment, have fixed to them aftrong ring, whofe plane is at right angles to the divifion o degrees on the plane of the pedeftal 5 within this ring flides the me= vidian, on one fide whereof are engraved the names of places, with their latitudes; and the other fide is divided into four quadrants of go degrees each: To the upper part of the ring, within which flides the. meridian, is fixed an inde, on which is a Ver-— nier’s {cale, ferving to fhew the parts of degrees on” the meridian; and to this piece is fixed a ring, by which the whole inftrument may be lifted. | Concentric within the meridian is the equinotlial ring; having on one fide the names of forne places’ with their laneudes : ; on the other fide the hours’of a day, each divided into every fecond minute; and the. infide of the ring divided in the fame manner. ‘This — ying turns on two points diametrically oppofite, — fixed at the divifions XII and XII, and the fame points are fixed on the infide of the meridian ring, — againit the diametrical divifions o and o, The equi- ~ nocual ring turning on thefe points, may be fhut up within the meridian ring, or fet at right angles to it, beyond which pofition it is not foflered s to pafs, ae there being two pieces fixed to the meridian which ~ {tops the equinoétial ring when in the faid pofition. The Bridge is a ftrait flat piece, fo fixed to the — meridian ring as to turn on two points in the direc: tion of the middle of the bridge, and oppofite to — the divifions go and go on the meridian, On one ~ fide of the bridge are the names of the months, with divifions to every fecond day; on the other fide are the figns of the Ecliptic, with their diftances gra- duated to every fecond: degree ; alfo the degrees and half degrees of deglination® north and ee ; and in the middle of the bridge is a flit, in which is placed a flider, with a hole in its middle, When ( 167 ) When an obfervation is made with this inftru- ment, ‘the latitude of the place counted on the me- ridian according, as it is north or fouth, diftinguifhed N. and S. mutt be brought to the index at top; the flider on the bridge muft be brought to either the day of the month, the Sun’s declination, or the _ Sun’s place, and then it will accordingly fhew the _ other two: The equinoctial circle muft be thruft out of the meridian, till it is at right angles to it. _ Then bring the beginning of the degrees on the ho- rizontal part of the pedeftal to the index there : | a the whole about upon the three feet, till the un fhines equally on both faces of the plane of the - meridian, the north part of the inftrument being ‘towards the north part of the world, and fet the horizontal plane level. Then fhall the dial be duly . rectified for obfervation. ‘It may be readily known when the plane of the meridian is directed to the Sun’s centre, by holding a piece of clean paper behind the meridian, and ob- ferving that the fhade of the fore part of the ring falls juft on the breadth of the infide of the back part ; and that the fhade on the paper is of the fame breadth with the thicknefs of the ring. Now keeping the three feet in the fame place, turn the dial about, till the fpot of light pafling thro’ the hole in the flider, falls on the circle which is divided into hours, €@c. in the middle of the in- fide of that ring which reprefents the equinoctial ; which will be among the morning hours, if before noon; and among the evening hours, if after noon’: then will the dial fhew thefe fol lowing very ufeful and pleafant problems, I. The fpot of light points out cally the hour of the day. M¢- II. The > ae SR ESP ET EIS TOI SEI em ee 7 : = Soon agen eae gh ee Ree = = ire SOE AS Ea Se é: SA in SSA _ Se et a - ee = sae SRST 2 — ur La - —— . =. - : ™ a SS Se Se ELLE er Bares: : r 1 T.7 t on. us rrr t itt x ¥ rr - = ae rt Es eyeynr-ror ery ty tye re opty leterrey ere + tT Tv x 7 rete re pees perk ARPETESSa est! rae = — -— te —: zs ae peste sea practi Fett eee te x = ( 168 ) ¥. The circle reprefenting the meridian, lies | exactly in the plane of the celeftial meridian ; and fo a thread ftretched over either face of it, draws a true meridian line. a ‘ ‘4 III. The middle of the Bridee pout “Se to q the true poles. : IV. The needle in the box tiers the variation — by the diftance of its end from the beginning of — the degrees there mark’d ; and is weftward, if the — north end of the needle be to the left-hand of the beginning of thofe degrees, but eaftward when to the right. | ee . The index on the horizon, points out the Sun’s Azimuth, which is to be reckoned from eatt or weft, if the circle on the horizontal pay is di- vided into four nineties. Vi. Turn the meridian about the plane of the horizon, till the Sun fhines equally on both its faces - as at firft, the three feet ftill ftanding in the fame place, Mid move the meridian towards % or from the Sun, till the fpot of light coming thro’ the hole in that fight which has the crofs hairs in it, falls exact- * ly on ‘the little hole in the other fight which will ~~ then be undermoft; and the index in the Zenith, points to the Sun’s altitude, among, the divifions of the meridian, By this inftrument, may the pofition of any wall be thus found: Let a flrait broad, ruler, whofe fides ate parallel, be applied to a wall, on which a verti-. cal dial is defigned to be drawn, and the two feet of the dial. mark’d A, A, be applied to the other edge of the ruler; then let the dial be reétified to the latitude of the ‘place, with the day of the month 5 be if» 489 y Re levelled, st andthe upper part e the inftrument that. wall, ufually called by diallers, The declination of the p slane. Or, if the Sun does not fhine, apply the legs A, A, tothe ruler, keep them in that po- fition, and turn.the upper part about, till the north end of the needle points at the variation; and then vill the index on the pedeftal fhew the fituation, This curious inftrument is of great ufe for the re- ~golation of clocks and watches, “by the help of the apparent time obferved by it (as fhewn above} and the equation of time engraved on the horizontal part E | of the spedeftal. It is alfoa very ready inftrument for Seika an horizontal dial duly: For after the apparent time is found by it, and the horizontal dial fo feated, that it may be turned about, and ftill be parallel to the horizon ; then move it round, the Sun fhining there- on, till it fhews the fame tie that the apart dial fhews, and then it is,truly placed, and may be there fixed to the pedeftal. And becaufe the latitude of the plaee where the inftrument is ufed, muft be known; there is en- eraved on the backfide of the meridian, or the un- derfide of the pedeftal, the latitudes of the cities, | and moft remarkable towns in England, and other parts of Europe. But if any gentleman pleafes to communicate to the workman, the latitudes of his country feats, __ they may be particularly laid down on it. Or if any gentleman about to travel, is pleafed to communicate the tour he defigns to take, he may have a catalogue of the towns in his way, and their Jatitudes, from Mr. Heath, with the inftrument, in order to eafe him of the trouble of fearching maps, globes, or geographical books. The ned about till the fpot of light fall as before; then’ index on the horizon will give the fituation of — . : h . ey { if > oa j a es! at) nf ‘ r iia! ie Laren Lt way t bey ' 4 res] Lig lsd i wt i nt a TYy es Se ee? ~~ = a _ - Sn = = Sat Teter ft. ttt Tr? ( 170 ) _ The variation of the needle may be found by the Theodolite, thus: Take the bearing of the Sun exaét- ly at 12 at noon, and the north-end of the needle pies the variation. Or, take the bearing of the Sun, either at the time of rifing or fetting; and then, fay : As the fine of the complement of the latitude, is to the fine of the declination; {fo is the fine of go degrees, to the fine of the Sun’s diftance from the. eaft at rifing, and from the weft at fetting ; and is always fouther- ly, when the declination is fouth, and northerly when north, And as much as this diftance differs. from that obferved by the inftrument, fo much is the variation: And if the bearing taken by the in- itrument be to the left-hand of that calculated, it is _ wefterly, otherwife eafterly. Or it may be found, by an horizontal dial, duly feated, without the Sun ; ; if you ftretch a thread on ‘that dial’s meridian line, and the inftrument placed near it, you turn the index about, till the telefcope is parallel to that thread ; for then the bearing fhewn by the north-end of the needle, is the variation. Befide the preceding ufes of this univerfal dial ; it may, with a very fmall addition, be applied in all refpects as a Theodolite, or Circumferentor ; or this dial may be aptly and eafily mounted on a Theodo- lite, and be taken off at pleafure. There is one inconvenience ufually attends the ufe of thefe inftruments, which in this may be remedied : From about an hour before, to an hour after noon, the paflage of the {pot of light over the equinoétial, forms with it fo acute an angle, that it is not very eafy to obferve the point where it croffes it; and, confequently, the preceding problems cannot be fo exactly performed, And juft at noon, the thick. nefs ee 4 - aes i 4 if (O78)? i Aeatt of the brafs fhades the flider and bridge 5 and fo no obfervation at all can be made. In this cafe, bring the beginning of the degrees to the index on the horizontal part, and Jet the hour be taken by the inftrument fome time before, which is remote from noon, whether before or after, on the _ board of the window of your ftudy, where you de- fg to ufe it; the index all the while pointing to the eerenning of the degrees, Lay a ftrait ruler to _ touch the feet marked A, A; and by its edge, draw on the window-board a ‘enic line, or make two points where that ftrait line fhould be drawn: And then, at any time that is very near noon, -by laying the ruler to the line or points, bringing the begin- ning of the degrees on the horizontal part of the pedeftal to the index, and applying the feet A, A, | to the edge of the ruler, as before; if you rectify the inftrument to the latitude and day, you may fee the true time either before or after noon; and juft at noon, the middle of the under part of the meri- dian will be thaded by the upper; and confequently the time of noon, is known, and determined, whe- ther it be before or after noon. If you are in a ftrange place, and the time be very near noon, level the inftrument, and turn it about till the north-end of the needle points at the varia- tion, and then it is duly placed, and you may work asin the laft. : Much more might be faid of this inftrument’s ufe, but my defigned brevity will not permit me to enlarge any farther thereon. The latitude of a place may be found by the common Theodolite, thus: Turn the plate of the in{trument fo that it be in a vertical pofition, in the piane of the meridian, which may be readily known by applying to the plate a {tring and plummet; with this pofition, Set the fixed fights horizontal, either by "5 ty? fewer ce crearar nan ag Ee =: ee dah ce « - 7 de. ass a Se mt re tr x . Ss rors: ry = ——_ : " - = - 1 se oe WES ct r ay i. ly Byty t SS ee x se ~ Lest eieses. Ranta age iy mn on etttesaa os. r Feige z toons: ty ztr a7 sr Sa _ =. x teeth oe Si) tie ey a Mersey = z ~ r Eplyhy tet “ x Ne Sb 2 a ee. by a level, or by the thread of a plummet.cutting® the degree at right angles to the fixed fights; then ‘a little before noon move the index fo thatthe Sun’s _rays paffing thro’ the hole in one fight, the fpot' may fall direétly on the middle line of the other fight; and the degrees cut by the index will fhew _ the Sun’s altitude at that time: As the Sun mounts higher, the fpot will defcend on the fight, therefore keep the index moving fo as to ftay the fpot on thé. 0g line, until the fpot be obferved to begin to rifea- bove the line, then obferve the degrees cut by the index, and they will be the meridian‘ altitude, and their complement to 90, will be the Sun’s zenith diftance; which on this fide the tropic of Cancer muft always be named fouth. | | _ Now having the Sun’s meridian zenith diftance, and his declination taken from tables, the latitude of the place may be found by this Rue. If the zenith diftance and deelina- tion have contrary names, their fum gives the lati- tude fought, of the fame name with the declination. _ . But, if the zenith diftance and declination have the fame name, the difference will be the latitude fought, of the fame, or a contrary, mame with the declination, as it is greater, or lefs, than the zenith diftance. A ie re a E ig x t. rar Whew ys ) $3 =9 se Oy 239) ei» er Fey Gey © Sm Ae yD ca ae ies Seen le RV } io Aa Dy eo - - y eae 4 ese” ' P ues Ee The defcription and ufe of ibe Pantographia, or bt ee Imitator. 2 HIS inftrument confifts of four rulers, two large and two {mall: The two great ones are joined at one of their extremities by a joint, ‘or cen- tre, about which they are eafily moveable. At the bottom of this joint is a little roller or cafter, whereon the inftrument is to bear: One ead of each of the two {mall rulers are pinned near the middle of each great one, and the other ends fattened by a joint, fo that in what manner foever the inftrument is moved, | the four rulers always form a parallelogram, having : two contiguous fides about as long again as the other two fides, The two longer, and one of the fhorter rulers have each a box fitted to them, that may be moved and fixed to any part of the faid rulers, by means of a {crew fixed to the box. Thefe boxes have each a cylindric hole, wherein may be alternately put three things; namely, a tracing-point, a port- crayon, that rifes and lowers of itfelf, according to the unevennefs of the plane worked upon; and, a fulcrum that {crews into the table, the top whereof. is a cylinder fitting one of the boxes: This fulcrum is the fixed point round which the in- ftrument moves, when ufed to copy with. . There are alfo other cafters on which the rulers reff, ferving likewife to facilitate their motion. On thefe rulers are divifions with figures, fhewing where to place the . 4 cham- a == = So Ip Keke Feta k eee . 7 . ie a te we Loe rerEr Pah Tes rn oe ap ene ee See Se Se EEE = Ty r arse ———— es rt ee 65 4363s oo TON TH 123 and 4, £5 4, $ 7 + > qo0 T9 753 thefe numbers de- note the propofed ratios between the copy and ori- ginal; thus, if the copy is to be half the length and breadth of the original, the boxes B, D, and A, are to be fet at the divifions 4 and C; then the | ~ fulcrum is to be put into B, the crayon in D, and the tracer into A: Ifthe length and breadth of the a ‘copy is to be 2 of thofe of the original, the boxes B and D are to be put to the divifions 3, the box A, remaining at the mark C, where it is to be fet in every operation ; the fulcrum to be put into D, and the crayon into B. And in like manner any other diminution, within. the limits of the divifions, may be readily performed. Cay When the copy is to be increafed in any ratio ex- preffibie by one of thefe numbers, the boxes B and D areto be fet to that number as before; the ful- crum put in B, the tracer in D, and the crayon in A; then the picture being put under the tracer D, and the clean paper under the crayon A, the copy may be taken as before. When the copy is to be of the fame fize as the original, fix the bevel edge of the boxes B and D, _ to the marks 4, and the box A tothe mark C; put the fulcrum into the box D, the crayon into B, and the tracer into A; then will the crayon B move over equal lines and fpaces with the tracer A, and, confequently, delineate a copy equal in fize to the original, ; And thus may any picture be accurately copied without damaging it in the leaft ; for the tracer may be paffed over the lines without preffing on them, or even touching them: But that this bufinefs of copying may be rendered as perfect as can be de- fired, it will be neceffary to be more circumftantial in es x oe per tyt r 9 oe ne Se oe in eee erty PSS Se ee Se ae ee ee vit. - ~ ee Pec as 2 a 0S Ee os 5 ries! oom Sn 8 rhs tye ee ee om a 1 a : or a a ne We | hy i i a a pa a aa soe es eee Se ( 176 ) in deferibing the ufe of chis inftrument, particularly. 4 fome appendages and cautions not yet mentioned,’ ~ In plate Vl. jig. 1. reprefents the plan of the in- if ftroment, with all the divifions ; figure 2 is a per- 4 fpective view of it on a table, in ‘fie proper pofition 1 for ule. The boxes A, B and D are placed for rer J ducing the original to one third of its fize, or as 1 to 3, fhewn in r the figure. The fulcrum f, ferewed - into the table, is placed in the box B; this fulcrum, as hitherto defcribed, is fixed, but a moveable one may be fubftituted in its room, — as fhall be fhewed — hereafter. | Over fig. 2, the different pieces fret to the rulers are feverally reprefented. The figures A and Ran | prefent the two boxes. Eis the tracing point that fits in the focket N, fixed to the boxes A and B. Thefe fockets has a little {crew O, ferving to fix ae tracing point when fec in the boxes, at phe ue height. Fioure F is the tube for the port crayon, G ‘ a the port crayon to be put into the tube Fy at has a {mall filken ftring fixed. to it, ferving to raife the crayon or pencil, "fo that it may not touch the paper 7 while it is moving from one place to another. This — | {tring is thus fed 3 when the crayon is in the box: D, pals ‘the loofe end thr ough the nase ‘in che uprighe pieces fixed at Z, S, X, fig. 2; then taking the end’ into the hand hol ae the iit A, the crayon may be raifed with the oreateft eae, | Henao it 1s wanted, even while the ‘inttrument i is moving. - But if the crayon is put into the box A, then the loofe end muft pafs through the holes in the pieces X,.S,: Z, and fo to the hand, which in this cafe will have hold of the box D. The ftring is reprefented in fig. 2. its length is al- ways the fame, however the boxes are placed, be- caufe it follows the direction of the rulers, a he C174.) The cup H above the port crayon G, fcrews on its upper part, and ferves to increafe ahs weight of the crayon or pencil, making it prefs harder on the pa when neceffary ; this is done by putting in | eaden fhot, or any fuch like weight The lit: ie wheel, or caftor, L, chat has a double flit or groove, x and y, 1s fixed to the ruler B by. the under groove x, when the crayon is put into the box B. But if put into D, the caftor or wheel L, then flips on the ruler D by the upper groove y. Misa wheel or caftor to be put on the ruler A, _ The fulcrum, fcrewing to the table, as mentioned ‘in the foregoing defcription, and reprefented in fig. 2. being proper only to copy fubjects of a middling fize; a moveable fulcrum rape teaeee by fig. P, is to be ufed when the picture is large. This fulcrum is a piece of lead of fufficient weight fo prevent its being difplaced by the motion of the inftrument. In the middle thereof is {crewed a pin K, like the fixed fulcrum [. The figure R is a little collar, ferving equally to either the fixed or moveable fulcram, on whofe pin it is put when either of them is placed at the box D: But is not ufed when placed at the box B, becaufe this is lefs diftant from the table. Little collars, of different heights, are alfo ufed in the fame manner to K and 1; the ufe thereof de- pending on the prudence of the operator, taking” care that the motion of the inftrument be performed with the utmott freedom. With this moveable fulcrum a picture or drawing o Jany dimenfion may be copyed: For the pidure being made faft on any table or plane, the fulcrum mutt be fo fituated that a part thereof may be copyed as far as the inftrument can extend at that time. Then on the picture and paper mark three corref- ponding i on each, to ferve as references for finding the pofition of the fulcrum in the copy, Fe- latively to what has been already drawn; move N | the Seater tree ee epee aPurert x* oe ¢ zt Hig page) ye Te an. — : a5 — 3 7 etree rf as ‘ tet t Es “= = mi Tas sip cn en oe Sa aa as A Ty r erty z Sa $e 0 SS TS cy Ty S a t Chetan the fulcrum towards the picture, and when the three points on each are found to correfpond, fix the copy: * in that fituation with a little foft wax; then con-. tinue drawing as far as the inftrument can extend, oi as before, repeating this operation till the whole is, ed, we he ufefulnefs of ae moveable fulcrum is eafily perceived ; for if towards the end of the operation both the copy and fulcrurn fhould reft on the pic- ture, it would be no inconvenience as they no ways. damage it. By this means alfo the extraordinary — length of the rulers is prevented, which are gene- rally but of abour two foot anda half; a greater: length would render them inaccurate, becaufe they would then be more fubject to bend and {pring It may happen, on account of the fize of the paper, or otherwife, that the copy will not be ina proportion to the original, expreffible by any of the divifions on the inftrument; in fuch cafe a method. muft be found to do without, by placing the crayon, tracer and fulcrum in a pofition anfwering to the re-. Jative dimenfions of the original and copy. In order to which it is neceffary to obferve, that. the fundamental principle, on which depends the ac. curacy in operating by this inftrument is, that the. fulcrum, crayon, and tracer, are always to ftand in a right line, in every pofition of the rulers; when-. ever they are fo, the copy will truly reprefent the original. By the following method it will be known if thofe three points ftand in a right line. Let the fulcrum, crayon, and + tracer, be included , between a doubled thread, as in the figures marked 1h, 25. 2, lange under the inftrument marked fig. 1: Hold thefe threads faft at the mark Ef and if the points are not in a right line, the thread will be bent at the box D, marked 2; this box muft then. be moved till the threads become parallel, by 4 touching = ~“* (179 ) touching both fides of the three cylinders, which will then be in aright line, This principle being obferved in the dofition of the abovementioned points, let there be given a picture or drawing of any dimenfion to reduce to a fize that is no aliquot part, or parts of the original ; then ope- rate.in the following manner. Examine, firft, i the given fize is greater or lefs than half the original. | ~ When lefs, always place ‘the fulcrum in the har B, the crayon in the box D, and the tracer.in A; thefe points being brought to a right line as before- mentioned, run over with the tracing point, A, the whole length or breadth of the original in a ‘ftrait line ; then examine whether the Ime: miade by the crayon agrees with the fize given, Jf not, and that the fpace run through by the crayon is lefs than the given fize, bring the box B nearer to the line B on its ruler, and the box D nearer the line D on its ruler. If; on the contrary, the line traced. by the crayon be greater than the given fize, bring the two boxes B and D towards the junction Z of the rulers B and D; and; by trials, the proper extent will be found. coll * By this method, a drawing of any dimenfion may be copyéd on any given fide, without regard being had to the divifions on the ruler. _ If the given fize be greater than half the original, then the fulcrum mult be placed in the box D, and the crayon in the box B. When the picture is fo large that the inftrument cannot extend to its limits, then a third, fourth, &fc. part fay be taken; proportioning the parts of the copy to thofe on the original; and working accord- ing to the foregoing directions,’ an accurate reduced copy thereof may be obtained, N 2 Te Fs ee as mn Gap a ae Se aS A ce cn a ES ae gh ee ee 2 eee ee oe ne ee ap ee x "tT ype Le La! tet Fr) : fH th SS alee ee “(180 fe T 0 find the ae ifions on the legs S B, s D. Let the lines AB, a On EG, GH, Fie: FA Plgte VII. ) reprefent four rulers, fol conneéted toge- | ther, that in any pofition of AB, AC, there may — always be formed a parallelogram, whofe fides are a As EG. ees HAL Now if: ACi 1s af any fixed fenigieli and éhe ra- 1 tios of AE and ED to AC be aflumed, and thro’ D be drawn the right line C D, rye A bil in 1B Required the length of A B. And AC: E Dita: m, Then ED=—x AC, Now CF:FD::ED: EB, by mila tri- | tag Or AC—ED: FD: :-ED : AB—AE. “EF Dx Hepes |e Put AC=r, Then AE=—r; and ED=—r. And r——ri—ri: —r:AB——r. Therefore nN a n a 7 mM C MC me ABxr—ABx —r—~a~—rrte—rro=—re. fant ne a BE na | ‘Therefore AB Xr—-ABX ~ ror r. > n ¢ Confequently A B= pra Sam Hence \ aa Let ROOAE 202 eae ( xi ) “3 gee AB ei Kem a when AE=>AC. 3 Alfo = air, when AC'= 1. PF. 4a . pp “eo | { . ‘ts | lithe ratioof AE and ABto AC were afigmed, to find ED. | Bo? | | Thea AB: AC::EB:ED. A a ~—6hr Or AB: AC::AB—AE: ED. Let AB: AC:is:2. ‘Then AB = £ KC. dytyt yet ~- = BL Ree Sent And— AC :AC:: = = AC——AC:ED. : —tl | Therefore w= (“5 seats), at ge od xr, Hence ED=1— . xir, when AB=2 AC. Alo E D— pax, when AC= 1. And hence the numbers in the following table were found. Where ED in the firft column, and A B in the third, are each compared to AC, their ratios being expreffed by the numbers in thafe co- * Jumns ; arid the numbers in the fecond and third co- lumns, are related to AC asthe unit; AE being {uppofed =o toz AC. SSS : pe eae a a es So es ck ce aie oO a ae eo OT Se eh ee ie an OS OS t=" A ta ( 182 ) A TABLE for thedivifions of the Pantographer.| When E D | Then AB When AB Then ED is pNee 1S PED) PS oh 1s’: 1s be put into B, and the crayor into A. FIN I &. . er -<-- al $ ; | } i Pm 1 f ' > | * | 5 | 3 d ‘ 4. Si P iy ’ ~# #4 Lege aie Sth: > Srp ns an nent openness excl s = : E ee ee 7 ety * , a SETS = es sates WGA iis: —————— AAC SS = Ee = = ——— SSS SSS SS SS SSS SSS SSS ——- = SSS SS = ——s == LSsssS_ WS SS SSS SS SSS SS = SSS S = = <> = i} HN SSS SSS —= SSS LSS == = ih } i ih SS SS SSS } W ) —— if Mh Yh yj = Hf th Ny} WAY) 1) i} if —— y tt Mh / y i i} 14 y i } iy MH Vj y We My i) Uy = SS i Ny it = SSS == SS Hi HN, Mi, YY; = = = : = z —S > SS SS — = S55 SSS =S== Ss A ze — SS: = Ss SS = = = : = 5 SSS — S SS Gj litt : = = ‘ SsSssS= . ’ == = = oe Sr ie SS = ————————————————— SS , SSS = SS SSS - SSS 3 . = SS : 3 j SSS SSS SSS ~ — — SSS) = ‘ =—— == — >= = : SSS — SSS SS = LSS —~ WSS SSS SSSSSSSSSSSSSSSSSSSSISSSSS * SS <= = — — = — > \ SSSSSSSSSSSSSSSESSSSSSSSSS SS : SSS =—S Ss —— = Sj SSSSS—>~a—_~_—sw—sw—soosss SSSSSE = LSS ; ; : ; q == SS = SSE == = SS SS . Be SSS SS== SSS SSS Ss \ SSSSsSs SS SSS —————SSSSSsssssss SS —S = = > = —SS a SSS SS SSS SS SSS SSS SS —— LSSSSSSs: = = —— SS >> — > SS SSS: SS LLLSSSSSSSSSSSSSES = SSS SS SS SSS SSS SS SSS SS = SSS = SSS SSS : : <= == = = : S yp => SSS = SSS SSS = SSS SSS = SS A, i SS = . 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