f ';.• '^•' V JJ- L. *^.: 3% ./ a? 5^> ftor-- -^ vT' ssassEsz •■■!K«'iy9i^>« MtaprtiMtfEiMii :.-.-Lil '^ J^" i >J^"-" ■i rTB[- «l !^^^ _■' ,^ ^■■^^■mwiJ-^ui^^^ii^ ^ '^— ' IJ w iJ i g i jbJ ^g— 1^^ MKiwuiimirra SSSSZSES szs2^:^^ss^sssr S2B^!SSSZ fliiii wBiirfS c^ rrfw-r MYiVfffcr^^ ^iWHinMisn glltfTfTTri> > y-^^ II ^ 1 JLJMJMMHU » J I . W L. l -qj 'I ILJ l " i LJ -|fcjr-l i rm i *t ^S.r^lJ^rrf^iri''?h^ ,^- ifMTfc'faiMrfT^it^^feTi "mrfUpHF^^, <^f0mmiti ULj W Linw i nm ■ I Ml fliMMi am ■(MKTC* ■«aM«fi>H'i> IiiimZ ^ rffi y- THE CONSTRUCTION O F TIMBER, From its EARLY GROWTH; Explained by the MICROSCOPE, And proved from EXPERIMENTS, In a OTeat Variety of Kinds: In five books. On the Parts of Trees ; their Vessels -, and their Encrease by Growth : And on the different Disposition of thefe Parts in various Kinds; and the Particularities in their Vessels. V/ITH figures of Their various Appearances ; of the Instrument for cutting them; and of the Microscope thro' which they were viev^ed. By JOHN HILL, M. D. Member of the Imperial Academy. LONDON: Printed for the A U T H O R ; And Sold by R.Baldwin, in Pater-Nofter-Row ; j. Ridley, in St. James's-Street ; J. Nourse, T.Becket, P. Elmslt, J. Campbell, in the Strand; and T. Davi?s, ia Rulld- ^treet, Covent-Garden. M.DCC.LXX. [ 3 ] INTRODUCTION. IT is propofed to fliew the Conftrudion of Timber : the Number, Nature, and Offices of its feveral parts ; and their various ar- rangements and proportions in the different kinds : To point out a way of judging, from the ftrudure of Trees, the ufes which they will beft ferve in the affairs of life ; and of adding fomething to their ftrength, and prefervation. The compofition of the whole; the variations in the difpofition, and the differences in pro- portion of the feveral parts, are, in many of the fpecies, fo ftrange, and in fome fo very delicate, that to fee them diftindlly there are required pieces of fuch an extreme thinnefs, and magni- fying powers at once fo great and fo clear, that it were vain to lead men into an attempt of fol- A 2 lowing 4 INTRODUCTION. lowing the experiments, without firft acquaint- ing them with the machine by which the pieces v/ere cut ; and the Microfcope thro' which they have been viewed. The Cutting Engine is an invention of the ingenious Mr. Cummings. The two or three firft were perfetfted under his own hand ; and they are now made for general ufe by Mr. Ramfden» DESCRIPTION of an INSTRUMENT for cutting Tranfverfe Slices of WOOD, for MICROSCOPICAL OBJECTS. A A. Plate I. Fig. i. reprefents a cylinder of tvory, three inches and a half long, and two inches in diameter ; to the one end of which is fitted B B. yf plaie of hell-metal j the fed:ion of which, with the manner of fitting it to the ivory, may be feen in Fig. 2. in which the feveral parts are marked with the fame letters as in Fig. i. C. is ^ plate of brafs, fitted to the other end of the cylinder ; through which and the ivory there INTRODUCTION. ^ there pafs two long fcrews, which take into the thick part of the bell- metal B B, fo as to fix both plates ftrongly to the ivory ; into which they are alfo indented, to prevent fuch fhaking as might otherwife happen after fwelling of Shrinking. D D. T&e Cutter ; whofe edge is a fpiral, and the difference of whofe longefl and fhorteft radii is equal to the thicknefs of the largeft piece of wood that the inftrument will take in. The loweft fide of this cutter mud be ground ex- tremely flat and true, in order that all the parts of its edge may be exactly in the fame plane ; and that the middle part of it may be applied clofely to the fiat circular plane left at the center of the plate B B, to preferve it in the proper dire<5tIon when carried round by the handle. . All that part of the bell metal, which the edge of tke cutter traverfes, is turned fo low as not to touch it, (fee the Sedion :) the middle of the cutter is about j of an inch thick, and has in it a fquare hole that fits on the end of a fleel axis P P, one end of which turns on a pivot in the plate C, the other end in the plate B B. This end has a conical fhoulder which fits into a hole A. 3 of 6 INTRODUCTION. of the fame (hape in the under fide of the plate, as reprefented in the Section. e e, A piece of brafs fomewbat in the form of an index, which is alfo put on the axis P P : this piece has a round hole in its center fo large as to admit of its being turned into any pofition with regard to the cutter ; and in order to keep it concentric thereto there is left on it a circular projection which fits into a cavity made in the lower fide of the handle, where it fits on the axis. (See the Sedion.) F. The handle 3 which is fo fitted on the axis P P, that it carries the cutter and the piece e e round with it. G. A Nut that fcrews the handle on its axis, and keeps the cutter flat to the bell-metal B B, when carried round by the handle, 0. — Is a hole nearly in Jhape cf the feSior of circle^ pierced through that part of the bell- metal which the edge of the cutter traverfes, and continued through the whole length of the ivory cylinder, truly parallel to its axis, and of an exadly equal width throughout, till it termi- nates at the plate c, H. reprefents ^ INTRODUCTION. 7 H. reprefents the end of a piece of wood of which fices are to be cut, and which is put into the cavity ', into the angular part of which it is gently preffed by means of K K. Two brafs fcrewsy which pafs thro' the ivory into the cavity 9^ and are made to prefs on the wood h by means of L. A key that fits into hollow fquares made in the fcrews K K. M. Afcrew that paffes thro' the brafs plate C, oppofite the middle of the cavity o-, and by means of which the wood h is raifed to the cutter. This fcrew has forty threads to an inch, and its head being divided into twenty-five equal fpaces, it is evident that the moving one of thefe divifions or fpaces will make the fcrew advance and raife the wood y6 jufi: one thoufandth part of an inch. N. An index that points the divifions on the head of the fcrew (M). The breadth of this index, from the one fiducial edge to the other, fubtends a divifion and a half on the head of the fcrew ^ by which means half divifions as well as whole ones may be accurately fhifted, and the 2000th, 1500th, loooth, 750th, &c. parts of an inch, truly eftimated. To render the A 4 effcd 8 INTRODUCTION. efFed of this fcrew the more certain, its point is turned round Co as to aO. very near the center, and a piece of ivory (fee Fig. 3.) is carefully fitted into the cavity 000, fo as to move freely therein without any lateral fliake, and to reft on the end of the fcrew M. This piece of ivory adling equally on every part of the under furface of the wood, will raife it towards the cutter with much more certainty than if the fcrew adled immediately on it. Several fuch pieces of ivory, of different lengths, (as reprefented by Fig. 3.) ought to be fitted to the inftrument, fo as readily to fuit the length of any given piece of wood. One piece of the full length of Fig. 3. muft have one end left rough from the file, that pieces of cork, agaric, the pith of wood, and fuch other foft fubftances may be cemented on it with fealing wax; in which cafe they can be cut into llices of a determinate thicknefs, as well as wood. Now if a piece of wood, whether round or of the fl:iape reprefented in the inftrument at (^), and of whatever fuitable fize, be put into the cavity 000, and gently prefTed into the angular part thereof by the fcrews K K, let it be raifed towards the cutter by means of the fcrew M. If / INTRODUCTION. 9 If the handle be turned to the right, the edge of the cutter will advance on the wood, and cut off fuch part as lies above the plane in which the edge of the cutter moves j and when the upper furface of the wood is thus rendered fiat, flices may be cut of any required thicknefs, according to the number of divifions that the fcrew M is made to advance. If the machine be made with due care, it will readily cut a thoufand llices in an inch ; and if the edge be good and very well fet, llices may be cut that are no thicker than the 1500th or even the 2000th part of an inch : but this requires management, much depending on the force with which the fcrews K K pinch the wood. It is not an eafy matter to procure an edge fufficiently fine for the above purpofe -, but with the very beft polhble, thin flices have a tendency to curl up into rolls, fo as to be unlit for the Microfcope ; to prevent which, a very flender fpring is made to prefs gently on that extremity of the flice where the incifion begins, fo as to keep it flat to the cutter : when this fpring is fet to its proper pofition, it is fixed to it by the fmall finger-fcrew I. And left the adion of this fpring fliould deftroy the flice after it is wholly 10 INTRODUCTION. wholly cut, and in paffing over the extremity of the cutter, the piece e e (which turns with the cutter) is fixed by the nut G into fuch a polition, that in paffing under the fpring it raifes it, and relieves the flice at the very inftant that the cut- ter has wholly done its office : and thus the flices are made to fall into fpirits of wine, in which they are preferved for ufe. In fome woods the pith fh rinks fo very fa ft that it is extremely difficult to keep it entire in flices that are thinner than 750 to an inch : to remove which imperfedion an inflrument, of the nature above defcribed, was made to fhift its own fcrew at every revolution of the handle, fo that very little time was left for the pith io flirink ; as a hundred flices could eafily be cut in a minute, and the pith was as entire as the wood. This inflrument had an index, which being fet to the numbers 500, 750, icoo, made it cut fo many flices to an inch. It performed extremely well, but was judged lefs fit for general ufe than that which has already been defcribed, it being more complex, and liable to diforder, as well as more difficult to manage. The ( INTRODUCTION. ii The compofition of the Microscope (which was made, by diredlion of the Noble Perfon who is plealed to be the Patron of this Work, and its Author ; by Mr. Adams, in Fleet-Street, Mathematical-Inftrument- Maker to His Ma- jefty) will be underftood by the annexed figure, Plate IL A DESCRIPTION of the VARIABLE MICROSCOPE. ABC, the body of the Microfcope, contains two eye glafles at A, a third near B, and a fourth in the conical part B and C. The end C fliews alfo one of the magnifiers fcrewed thereto. Hence the body of this Microfcope exceeds thofe hitherto made, which have only three glalTes ; by encreafmg the field of view, and tlie light ; as well as affording an occaficnal oppor- tunity of increafing the magnifying power of each particular object glafs : which is performed by pullinp; up the part A E, and the outivard tube A B : the firfi: feparates at A, the other at B. Another advantage attending this inftrument is, that any two of the magnifiers may be ufcd at thQ fame timej in this manner: fcrew the 2 button 12 INTRODUCTION. button b to the part c of the button ^, and then fcrew both together into the body at C ; the magnifier there reprefented being firft removed. There are feven of thefe magnifiers -, two of which are fhewn at a and b : alfo fix filver fpecula, each having a magnifier adapted to the focus of its concavity ; one of which is repre- fented at e J thefe are to be fcrewed cccaflonally to the body at C. Every one of the feven but- tons, a by may alfo be ufed with any one of thefe fpecula, by fcrewing the lower part of the fruf- tf um of a cone, which is figured at d, upon the prominent fcrew on the filver fpeculum at ^, and then fcrewing the part c of any button b into its upper end, and all together into the body at C. Note, The glaffes are marked i, 2, 3, &c. and the leafl number is the greatefl magnifier. The body of the Microfcope A B C is fup- ported by an arm F, into which it may be put or taken out occafionally, and may be faftened by the fcrew f. This arm is fixed to the bar G G, which may be raifed or depreffed by turn- ing the large ivory head I, (the fcrew at H being firfl difchargcd.) G G Aides clofe to the upper part of the long bar K L, which laft is firmly fixed INTRODUCTION. 13 fixed at N and N to the tooth-wheel N O N ; this wheel is fiipported by four fcroles whofe extremities are connedled to an horizontal circu- lar plate n, which gives an horizontal motion to the wheel, the bar K L, and every other part of the Microfcope which is conned:ed thereto ; the whole being fupported upon the pillar M by the three feet P P P. The annexed figure of the Microfcope is deli- neated from its perpendicular poiition, being that which affords the beft reprefentation of its feveral parts i but there will be no difficulty to conceive, that on turning the key S the pinion that works in the teeth of the wheel N O N will give the bar K L, with the Microfcope and all its appen- dages, any obliquity or inclination that may be required. The ftage, D D D, with a hole T In the middle, is defigned to place objeds on for ob* fervation j thefe being firfl: fixed in an ivory ilider. No. i. or upon a flip of glafs, No. 2. or they may be placed upon one of the round glall'es which arc fitted to the hole at T. The concave mirror Q^Q^turns vertically on the extremities of the femicircle g^ and hori- zontally in the cylinder h, by which means it mnjr 14 INTRODUCTION. may be diredled (o as to reflecft the light thro' the center of the ilage at T, and thence thro' the body of the Micrufcope to the eye at E. The ftage D D hath a conical pin which fits a hole in the Aider W, in which it may be turned fideways, fo as to examine any obje(5t too large for the field of view. The fcrole y6 R has alfo a conical pin fitted to a hole in the Aider V. By means of the llider W the ftage D D may be readily fet to its proper diftance from the magnifier in the button at C, and then by turn- ing the large ivory head I, the body of the Mi- crofcope may be brought to its diftindt focus. If this be not thought quite fufficient, tighten the fcrew at H ; and then by turning that at X it may be adjufted to the eye of any obferver with the greateft precifion, and by the help of the fiider V a proper fpot of light may be readily obtained. No. 3. is a cylindrical tube, in which an in- ner tube k is forced upwards by a fpring : its ufe is to receive an ivory Aider No. i. or a glafs llider No. 2. the objecft being placed in the center of the hole at ;;;, and the llider put between the plates /j and /. The hollow at ^ is INTRODUCTION. 15 is to receive a glafs tube for confining a fmall water animal, to fee the circulation of the blood. If the animalcula in fluids are under confi- deration, or any very minute infed, it will fome- times be neceifary to exclude part of the light which is refleded from the mirror Q^by putting the cone No. 4. upon the bottom i of No. 3. it being firft put into the ftage at T. The nippers. No. 5. are for confining any objeft, and are to be placed in one of the fmall holes near the extremities of the ftage, or in the focket r, at the end of the chain of balls. No. 6. as the pointed nippers /, which hold an opaque objed t v. The ilage D D being re- moved, and one of the filver fpecula fcrewcd to the Microfcope at C, the Aider W brought near to the flider V, the ilem x of the .iiHar belonging to the chain of balls being put into the hole at W, the balls may be re;'di!y managed to give a proper direction to the objesfl v t, and the obferver's back turned to the window, [q that the refledtion from the mirror of the Pd.y behind or one fide may fall upon the filver fpecu- lum, and thence be returned upon that part o£' the pbjedl i v which is to be examined. No. 7- i6 INTRODUCTION. No. 7. is a box containing Ipare talcs, to fupply the ivory Aiders. No. 8. is a double convex lens, to be ufed as a magnifier in the hand. Laftly, Remove the body ABC, and put the flage D D into its place in the arm F -, put the pin of No. 9. into the hole at z, in the top of the bar K L ; place an objeft upon the ftage ; and any one of the magnifiers before defcnbed may be fcrewed into the end e of the Hiding bar eg. In this flate of our variable inflrument we have a fingle Microfcope to which the above apparatus is applicable : three magnifiers are added» to be ufed only in this application. There are likewife added to the apparatus, two glafs planes broader than that of No. 2. and two others with hollows ground in them. Alfo a few flat, round glaffes, of different colours, which fit the hole T in the ftage D D : and a watch glafs, fitted to the fame place, for ©bferving the animalcula In fluids j And a fet of glafs tubes, THE INSERT FOLDOUT HERE [ 17 ] THE CONSTPvUCTlON O F T I M B' E EXPLAINED BY TUE MICROSCOPE. BOOK I. of the conftituent Parts of Timber. CHAP. L Of the Number of Parts in Trees, and the Manner in which they are difpofed. 7 "^ H E compofition of Wood is bed fee a in a Shoot of two years and a half growth : and the moil dillindt and pleafing view of the feveral parts, as they lie together, is to be obtained by placing a very thin fiice, cut tranfverfely from fuch a Shoot, before the fifth glafs of the reflecting Micro- fcope. B Greater i8 The Construction of Timber Greater Powers, and another Apparatus, will be required for the examination of every part of this compofition, feparate ; but before we enter upon that enquiry, it is heft to take this general view of all together. The whole Slice confifts of feveral concentric Circles, of different fubftance; with veffels, alfo of different kinds, interfperfed among them. The Parts are thefe : 1. The Rind. 2. The Bark. 3. The Blea. 4. The Wood. 5. The Corona, or Circle of Propa- gation. 6. The Pith. Thefe lie immediately within, or under one another : and in, among, and between thefe, are difpofed the Veffels, which feed the whole ; and fome of which contain the juices, that give the Tree its peculiar qualities, and virtues. Thcfc Explained by the Microscope. 19 Thcfe VeiTels are of five kinds ; 1. The Exterior ) 2. The Interior > Juice-Vessels, 3. The Intimate J 4. The Sap-Vessels. 5. The Coronal. Of thefe, the firft: are placed between the Rind end Bark j The fecond, in the fubftance of the Bark ; The third, in the fubflance of the Blea ; The fourth, in the fubftance of the Wood ; The fifth, in the Corona, or Circle of Pro- pagation. Befides thefe greater Veflels, the feveral parts themfelves are vafcular j but their Tubes are of another kind j and will be confidered when we examine the conrtrudtion of thofe feveral parts. Other Glafles will be required for this : they fcarce appear in the prefent View -, which is limited folely to the arrangement of the con* ftituent parts together. B 2 ^ The ^o The Construction of Timber The tree In which thefe feveral circles lie in the happieft v/ay for obfervation, is the Scarlet Oak of America. If a flice be cut from a two years and a half Shoot of this tree, in May ; the parts and veflels juft enumerated will be (cen as they are reprefented in Plate III. and this with great diftindnefs and precilion. Where this tree is not at hand, fuch a flice of the common English Oak will very well fupply its place, the parts lying nearly in the fame manner. a reprefents the Rind, dry, and very thin. ^ the exterior JuIce-vefTels. Thefe are placed in round clufters ; they are woody ; and contain a thin, whitifli, watery juice, of no tafte. c, the Bark. This confifts of a multitude of jfilmy bladders, ranged in circles, one behind another : they are elliptic, thin, and brownilli ; . €nd they hold alfo a watery juice. They are conned:ed together, and arife in thefe circles one < behind another. if ^, the Explained by the Microscope. 21 d, the interior Juice-veflels. Thefe are ar- ranged in oval cluders, a very tonfiderable num- ber of them together. They are of many times the diameter of the preceding : their coats are woody ; and they contain a thick, gummy, brown juice, of an auftere, ftyptic tafte. This gives the virtue to the Oak Bark, as an aftrin- gent ; and its quahty, fo ufeful in tanning animal hides. e reprefents the Blea. This confifts of con- neded circles, which have, in fo thin a piece, viewed perpendicularly, a great deal of the ap- pearance of the bladders in the Bark -, but they are in reality of a different nature, as we fhall fee, when each part is examined feparately : thefe circles are indeed tranfverfe fedions of elliptic velTels, arranged clofely lide by lide to- gether. They are equal in their whole diameter to the bladders of the Bark ; but their cavity is much lefs, becaufe their fides are thick. y fnews the intimate, or mofl: inward Juice- veflels of the Oak : they are fomewhat larger in diameter than the conflituent veflels of the Blea ; B 3 and 22 The Construction of Timber and they fland fingly, not in clufters, as the two former : they contain a thick and alnriofi: con- creted brown juice, more auftere than that in the veflels of the Bark : and it is from thele the wood of the Oak polTeiTes the fame auftere and aftringent quaUties with its Bark. g. In the whole fpace from ^ I to ^ 2 we fee the Wood. This is compofed.of five con- centric circles, terminated by fo many undulated lines. Thefe are the feveral coats of Wood, added from feafon to feafon. It has been fup- pofed that each circle is the growth of a year ; but a careful attention to the encreafe of wood has fliewn me, beyond a doubt, that two fuch are formed each year ; the one in Spring, the other foon after Midfummer. At each of thefe times the Branch ftioots out in length ; and whenfoever that is done, the Shoot of the pre- ceding feafon gets an additional coat in thick- nefs : I ihsll therefore be permitted to call thefe, infte?d of Year Circles, Circles of the Scafons, The Branch from which the prefent feclion was taken, having been of two years and a half growth, there are found in it five fuch circles. The Explained by the Microscope. 23 The compofition of the Wood is of vefTels half obliterated, by the growth of their fides filling up their cavities inwardly; and fweliing out in the fame manner externally. The whole interftitial fpace being thus filled up, the very forms of them are by degrees loft. At h are {hewn the Sap-vefiels of the Oak. Concerning which, there have been ftrange mif- takes. But it is not my purpofe to point out where others have erred ; only plainly to lay down what I have it^Wy and what the objeds themfelves are ready to make evident to every one. Thefe vefTels arife in the fubdance of the Wood, principally towards the outer edge of each circle. They are very large in the outer- moft coat ; and fmaller in the others : iind there are alfo irregular ranges of them, rimning thro' the thickneffes of the circles; hefide thefe prin- cipal ones of the outer courfc. They have folid, and firm Coats ; and they contain in Spring and at Midfummer, a limpid liquor, like watar, tut with a flight acidity : at all other feafons of ^ 4 the 24 The Construction of Timber tlie year they appear empty, their fides only being moiflened with the lame acid liquor. Thofe who examined them at fucli feafons, thought them air-vefiels ; and in that opinion, formed a conftruiftion for them, which Nature does not avow. i iliews the Corona, or Circle of Propagation ; a part of the utmoft importance in the Vegetable Oeconomy ; fince from it arlfe the branches, and encreafe of the tree : no Vegetable is without It 3 nor have the figures of thofe, who have drawn the parts of Plants, failed to exhibit it, as a portion different from all others : yet, till this occafion, it never had a name. It is in the Oak an undulated circle -, and the undulations of all the other circles take their rife from it. It con- tains diftindly two kinds of vefTels ; a larger, k, which are pale ; and a fmaller, which are browner; too-ether with an intermediate mat- ter : this lafl is not vafcular, but compofed, as the bark, of filmy bladders. The larger order of vefTels contain a fomewhat acid juice; the fmaller order, a very auftere liquor 3 and the intermediate fubfcance, pure water. / reprefents 0^1^ ^1-3 b / d '-' /■' f /'' .--'' Ji- ini Explained by the Microscope. 25 / reprefents the Pith. This takes the fame undulated form in its outline as the Corona, which every way inclofes it : its appearance is very pretty : it feems to confifl of rings, with iingle, double, and interfecfling outlines ; but the reality is otherwife. The whole is a compages of little, hollow, white films, arranged, |fide by iide, acrofs the entire fpace, and having others of the fame kind, and form, beneath them ; through the whole length of the Shoot. m fhews the entire Slice in its natural bignefs. Such is the conftrudtion of a Shoot, and fuch the diipofition of the feveral parts : we may now proceed to their feparate examination. CHAP. 26 The Construction of Timber CHAP. II. The Manner of obtaining the Parts of a Shoot feparate. THE enquiry into the ftrudure of each feparate part of the Shoot, is a matter of much greater care and attention than the former : I will not fay, of difficulty ; for every thing yields to a determined mind : but time and application will be required. The method I have ufed is this ; In the beginning of April I take a quantity of young branches, from the Scarlet Oak, and other trees. Thefe are firft cut into lengths, of the growth of different feafons ; and then part are left entire, part fplit, and the reft quartered, la this ftate they are put into a wicker bafket, with Explained by the Microscope. 27 with large openings, or of loofe work ; and a heavy ftone is put in with them : a rope is tied to the handle of the baiket, and it is thrown into a brook of running water : at times it is taken up, and expofed a httle to the air -, it is frequently {hook about under water, to wafli off filth ; and once in ten days the flicks are examined. By degrees, the parts loofen from one another j and, by gentle rubbing in a bafon of water, juft warm'd, they will be fo far feparated, that a pencil brufh will perfect the biilinefs ; and afford pieces of various fize, pure, diflincfl, and clean. One part will, in this way, feparate at one time, and another at another : but by returning the flicks to the water, and repeating the operation, in ^ courfe of four or five weeks, every part may be obtained diflind:. They are bed ex- amined immediately ; but as one widies to pre- ferve them for repeated enquiries, it may be done in this manner. Diffolve half an ounce of Alum in two quarts of water: drop the pieces, thus feparated, for a few moments, into this folation -, then dry them upon 2? The Construction of Timber upon paper, and put them up, in vials of Spirit of Wine. Nothing but Spirit of Wine can pre- ferve thefe tender bodies ; and, till I found this method of hardening them firft, that liquor often deftroyed them. CHAP. III. Of the Construction of the Rind. T has been cuflomary to diftinguifli the two outermoft coats of a tree by the names Outer, and Inner Rind ; but as we have the two words, Rind and Bark, in common ufe, it may be more diftinct to apply one of them to the one, and the other to the other. The Rind, or outermofl coat, being feparated Tom the reft, and cleaned, appears before the 4icrofcope like a piece of a white cobweb. It is to be examined, if freih, in water 5 if pre- ferved, in fome of the Spirit wherein it is kept ; being laid in a little ciftern, hollowed in a flip of Explained by the Microscope. 29 of ground glafs. The happieft view of it will be had by combining the fixth and feventh magni- fiers of the Microfcope here figured. Although this Rind be by far the thinned of all the parts, yet it is compofed of feveral coats ; one laid clofely over another, and all of the fame kind : the great difficulty is to obtain one of them abfolutely feparate. In that ftate it appears fcarce more than a fhadow, or a mere delineation of lines upon the glafs ; but without this, its- true conftrucftion cannot be known. The piece of Rind reprefented at Fig. i. In Tab. IV. ihews the necefilty of this exadnefs : the part of it at a is one coat only ; at b, two lie over one another i at r, three : in thefc two laft portions there is a great deal of confufion: but at a the real flrudure of the part is perfedly diftind. It confifts of a feries of longitudinal veiTels, and a filmy fubftance between them. It might feem that there are alfo tranfverfe vefTels going at fmall diftances from one of the longi- tudinal ones to another ; but this is a deception : a clofe examination will fhew, that thefe are only fpaces between part and part of the film. A larger 30 The Construction of Timber A larger power of magnifying being ufed, by changing the fixth for the fourth object glais, fWl keeping on the feventh, we fliall fee the difference between thefe empty fpaces and a vaf- cular flrudlure, very plainly, as at Fig. 2. throughout the courfe of thefe innumerable vef- fels, to pour their fluid into the interftitial mat- ter ; which fwelling with its quantity, like a fpuI^ge with water, prefifes every part outward and upward into growth and thickncfs. It were vain to feek them in the Winter Blea ; they are fhut by its contraction ; and tho' a little water keeps them in that ftate at thefe times of the year, the ocean could not at an ill feafon open them. Even in frefli pieces of the Blea the very form of thefe veflels is lofty, as foon as their juices leave them. Where-ever a piece is care- fully and lightly torn off, the Microfcope fliews its veflels in their cylindric form at firfl: j and fomething of their mouths is vifible in the more perfed: end of the piece ; but where they have been broken, and their juices let out> they col- lapfe, and nothing but a kind of flat whit^ thread is dutinguiihable. Fig. 3. a i> c, Ther 48 The Construction of Timber The Willow was felefted to fhew the iife thefe vefTels have in the Vegetable Oeconomy; becaufe in that light and loofe wood the mouths are very diftinguifhable : but there are other kinds in which the general conftrudion is more evident : the Pear is one : in this firm wood the vefTels are much plainer, though their mouths are lefs ; they differ alfo in colour from the inter- mediate matter ; for they are browniili, while that is pure white ; and being firm they are lefs liable to contra(flicn. I cannot tell whether forrie eyes diftinguifh better by the Microfcope than others ; whether the precife focus is lefs eafily found by thofe not fo much accuftomed to the Microfcope ; or whether there be any other advantage which that great nurfe of aptnefs. Practice, gives ; but to whatever it be owing, I have found it very difficult to (liew fometimes to others the things myfelf have feen moil: clearly : and I have named it in the prefent objetft becaufe it once afforded a remarkable inftance. The Explained by the Microscope. 49 The Blea of the frefh Willow appeared tp a Very careful obferver all ore fabftance ; the mouths in the velTels were feen, but not the dif*- tindion of vefTels and Flock. But a piece of the frefli Blea of Pear Tree then was placed in view, and while we looked at it, the natural contraction from the evaporation and lofs of the fluid con- tained in it, began ; and the floccofe matter fhrank fo much fifter than the velTels could, that though the ends had been cut even at firft, they were foon fo altered that the veflels flood out far beyond the Flock, and fhewed their form and feparate nature moft diflindly. In the Ozier, taken in its feafon of quickefl growth, in Spring, the Blea affords thefe veiTels yet more diftihdly even than the Willow; but the matter is more dinicultly managed ; for they are fo tender, fo foftj fo watery, that 'tis fcarce poffible to keep them together. Fig. 5. {hews a piece of it ; in which appears this farther dif- covery -than had been made before, that the mouths of the Blea vefTels all open upwards^ D In 50 The Construction of Timber In a piece yet farther magnified by a com- bination of two of the moft powerful objccft glafles, and with the advantage of a room con- ftrufted purpofely for this fervice, a degree of light was made to penetrate the very fubftance of thefe veiTels. The firft appearance it ex- hibited was that of many Cells or Blebs, fuch as we have feeri in the Bark and Rind ; but on more obfervation the appearance of thefe Cells was found to be neither equal nor regular : Nature has nothing to do with fo wild con- flructions as feemed to (hew themfelves here : the truth was at length difcovered : thefe feem- ing divifions altered their places j and were found only to be fmall portions of a watery Sap, which the contradion of the part had prevented from efcaping with the rert, at the mouths of the veiTtls, This appearance is given at Fig. 6. and may be a very necelTary lefTon againft hafty judgments. A Veffel feparated from this Ozier Blea is ihewn by itfelf at Fig. 7. 'Tis ftrange that the coat of veffels fo tender iliould be fo thick in proportion to their cavity j but this is the lea^l CQmpa(5t of all Blea veffels. CHAP. Explained by the Microscope. 51 CHAP. VII. Of the Wood. AS we proceed into the more inward part of the Shoot, in whatfoever Tree, the conftrudion becomes more difficult of ob- fervation : the parts are harder, and lefs free to feparate one from the other ; but with due care thefe macerations will afford, from one kind of tree or other, pieces which will difclofe their inmoft ilru6ture. Many muft be examined to find fuch j for it is not always in the Shoots even of the fame fpecies thefe happy objedts may be found ; the different forwardnefs of the feafon, the greater or lefs progrefs of the Sap, and even the more or lefs healthy ftate of the particular Tree, all afford variations, and render the beft fometimes inferior to thofe naturally much below them, D 2 The ^2 The Construction of Timber The common Pear Tree has afforded the inftance from which the prefent views are given. A piece of the wood of this tree, clean, pure, and perfedly feparated from other fubftances, is {hewn at Plate VIII. Fig. i. nothing can be fo fimple as its ftrudiure : tho' difficuh to ob- tain, there is little for obfervation in it when we have it ; only that trurh is always valuable : and when we know the compofition of the wood in one tree, we can underfland it in all. The Wood then is fcarce any thing more than an arrangement of plain and fimple tubes, re- fembling the tubes of the Blea; but that there are no mouths in them ; nor is there any of the interftltial fioccofe matter between them more than what fills the very fmall vacancies left by the roundnefs, between tube and tube : nay, even that difappears as the wood grows liarder ; and finally, in fome trees, even the tubes themfelves : their coats thickening both on the outfide and within, 'till neither cavity nor interflice remains, but the whole is become one firm fubflance. 5 This Explained by the Microscope. ^^ This may be feen in a tranfverfe view of the common Oak ; fuch being chofen as has pro wn on clay ;. for that from gravelly foils is much lefs compad:, lefs weighty, and of much lefs ftrength and value. In the Pear, and in moH: other Trees, fo much of the vafcular appearance remains in the Wood, as always to make it ealy to underfiand the ftruc- ture : we always fee vefTels, tho' with fmall apertures, arranged in lines the one behind the other, in m.any feries ; adhering firmly, and leaving fcarce any interftices. When a piece of freih Blea'is torn from a Shoot, we have obferved that at the ragged end, where the vefiels have been broken off, they lofe their form ; collapling, and no longer ap- pearing any thing more than flat threads : but 'tis not fo with the more firm and folid vefTds which compofe the Wood : they feparate indeed in a piece torn thin, but they keep their form and roundnefs, ^nd break all together ; nob one by one ; nor forming a kind of pyramid, as jn the Blea; but an equal, even termination. A D 3 piece 1^4 The Construction of Timber piece of the frefli Wood in this viev/ is given at Plate VIII. Fig. 2. At Fig. 3. is the reprefentation of a piece of the wood of the Bauhinia Aculeata, whofe dif- ference appears very ftriking ; but 'tis merely that of greater and lefs : the vefTels in this are extremely fmall, vtry hard, and laid unufually clofe together. The v/hole viewed with the ufual powers of magnifying appears one com- padl, uniform mafs j but greater glaffes fhew it formed jufl as the others ; only that there is fo very little of the interflitial fubrtance, that even in the youngeft pieces the veflels leem to fill the wiiole fpaces, by fwelling into them. At Fig, 4. is reprefented a fingle vefTel of the wood of the Pear, clean feparated from the other parts : this may be viewed all round, and thence wt are confirmed the wood veflels are mere clofe canals, with no lateral apertures. The plain and fimple hollow is alfo very well feen in thefe fingle veflels. Art would in vain attempt to procure fuch : they are too fmall to be the ob- jects either of the hands or eyes; but there never fail to offer fome of them among the variety ~W0 0D Ti.S. / 3 '2 5 4 - Explained by the Microscope. ^^ variety of macerations ; efpecially of fuch as have been rubbed about often with the hands. At 5. is a fe^lion taken tranfverfely from the bottom of Fig. 2. and at 6. a view of the Hke kind from the Bauhinia, Fig. 3. In the firft we fee a little remain of a fpungy fubftance between the vefTels : at 6. there fcarce is any. C HAP. VIII. Of the Corona. 9' I " I S ftrange that among all who have -1 written on the conftrudtion of Trees .and Plants, the Circle which furrounds the Pith, and feparates it from the Wood, altho' different in a high degree from both, and of a com- pofition not at all refembling either, fhould yet have had no notice, and no name. It is indeed D 4 the 56 The Construction of Timber the moft important part in the whole vegetable fabric; for *tis from this alone propagation and encreafe by Branches, Buds, and Shoots, is carried on. It has been a cuflom to fuppofe the Pith of Vegetables to be the part in which thefe v/on- derful fources of increafe refide : but this theory fhrinks to nothing before a careful enquiry. The flate of the Pith in young Branches will be fliewn in a fucceeding part of this Treatlfe ; and it will be found difcontinuous from the original Pith of the Trunk j and fo far from proceeding from it before the other parts, that it is in reality pofleiior to fome of them in the time of its formation. This important office of encreafe being given to the part to which it belongs, we ihall fee that the Corona is in every fsnfe, both of condrudion and ufe, an objedt very v/orthy of a careful examination. We have hitherto been employed about parts of Plants Vv^bich are perfedly uniform in their conftrudion. Nothing can be more fimple than the compofition of Wood; and if in the Blea and in the Rind there be a more elaborate flruclure. ExPLAINLD BY THE MiCRCSCOPE. j^ ftrud:urej ftill it is the fame in all the Blea;- and in the Blea of all Trees. Here we have ia matter perfedly different j the Corona is no£ uniform, but confifts of a variety of parts : nor is their nature or their difpofition the fame in all Trees. It is not Grange this Circle iiaould fo differ from the others 5 for they form and con- fiitute only one part of the Shoot ; but in this lie the rudiments of the v/hole : and the Branch which is to contain all thofe parts, is to receive them only from this Circle. The Corona then is a rino: ufually more or lefs angulated in its out-line, placed between the Wood and the Pith in all Vegetables. The general Circle is cellular, com.pofed of Blebs and veflels, as the Bark and Rind, and is peifeclly of their nature ; only that at diiTcrent diflances are difpofed among it oblong clufters of different veifels. Thefe cluflers are ufually eight or ten in number; and give origin to the angles of the Corona. They arc not uniform or of one kind of veifels, as in thofe in the Bark, but each has two diflind: forts ; the exterior ones anfwerin^ o to the Blea, and the interior to the Wood of Trees : and within each of thefe are alfo dif- pofed 5^ The Construction of Timber pofed velTels not unlike thofe in the Blea and Wood, and often even larger than they are found in thofe parts in the Shoot. Thus we fejs that each clufler of the Corona is compofed of all the effential parts of the fuc- ceeding Branch, and that the intermediate parts of the circle are abfolute Barl^ and Rind : they are ready to follow and death the clufter when it goes off in the form of a Shoot ; becaufe it will then need their covering and defence, tho" in its prcfent inclofed flate it does not. It is from this conftruftion that a Tree is at all times, and in all parts, ready to fhoot out Branches ; and every Branch in the fame man- ner to fend out others : for the whole Trunk, and the Branch in all its length, have this courfe of eight or ten cluflers of eflcntial vefTels ready to be protruded out i and the proper and natural integuments as ready to cover thcn:;i. In fome trees thefe parts are more evident, in others m'ore obfcurely arranged ; but when their nature is known, there is none in which they may not be found. The Explained by the Microscope. 59 The Oak is not one of thofe trees In which they are moft confpicuous and diftin(5l ; yet will the moft curfory obferver perceive, in a tranf- verfe fediion of a Shoot of that tree, that the circle immediately furrounding the Pith Is per- fcdly diftlndt,- both from the Pith which it enclofes ; and from the Wood which furrounds it. A fedion of the Oak is given for this pur- pofe at Plate IX. Fig. i. and near it, at Fig, 2. is placed a fedion of that tree, in which, of all that I have had the opportunity of examining, this circle is the moft diftindl. This is the Parrot Wood of the Weft -Indies, the Bocconia of Boranical writers. It fcems formed to lay open this great myftery of Nature -, for nothing can be fo palpable as the conftrudlion : 'twere well if this fpecies were always at hand in Europe ; probably it will be foon : in the mean time, the only Vegetable wherein the parts can be feen In a manner any thing refembling this, is an herbaceous Plant, the greater Celandine j to which indeed this Bocconia is in its Botanical charaders, as well as in its inner ftradure, very Bearly allied. This Co The Ccnstruction of Timber • This tranfverfe {cSiion of a Shoot of the Bocconia is given at Plate IX. Fig 2. With what fuperior beauty muft it appear f om a fr-illi Branch : for this was from one brought from Jamaica, and rendered manageable to the knife by a long infufion in water. We fee here the Rind ^, with its Bark underneath, ^; and the Vafa exteriora and interiora evidently mark'd iri them. Beneath thefe, at e, lies the Biea, per- fe<5t]y diftinguifhable from them, but fcarce at all from the W^ood, f, the Branch being very young and tender. But even in this date the part immediately within the Wood is mod: pal- pably diOindl : its fubflance, ftrudlure, colour, every thing, fliew that it is neither of the nature of the Wood, nor of the Pith : equally unlike both : and within this, but extending each way beyond it, are thofe cluflers of veflels which we find in all Coronas, tho' lefs diftind : thefe intrench upon the Pith one way, and upon the Wood itfelf another ; being in their nature and •Oaice of much more importance than both. -At /b is fhevvn the fubftance of the Ring o/r Circle, the irr.mediate matter of the Corona.; and at /; the cinders of vefTels which at their ? ': egrefs Explained by the Mici^ioscoPE. 6i egrefs from the tree are to form Branches : thofe the matter of the Corona always follows out, in quantity enough to cloath them. One Cl'ifler, feparated from the Ring, is reprefented more enlarged at Fig. 3. In this we palpably fee the fubicance of the Blea and the Wood, and yet more evidently the vefTels of that latter part. At a the loofe and open texture of the Blea cannot be m.iflaken by any who are at all accuflorned to thefe obfervations : at b the clofer ftrucfture o^ the wood is perfedly difclofed : and at c a pait of the fame wood furrounding the great vei ■ Is ^ bui: of a fcfter fubftance than the other, that it may not be capable of prefling thofe veffels, on whofe free courfe the growth of the whole Shoot, to arife from this clufter, perfectly depends. At d the great veffels themfelves are llv^wn, not at all exaggerated by lancy, or thr rag- of fyftem. It is juft fo they appear, and wfll always appear j even in the herbaceout Celan- dine ; as well as in the arborefcent Parrot- Wood. At 6z The Construction of Timber At Fig. 4. is given alfo an enlarged view of the fubflance of the Corona ; in which, as in all jufl: opinions, the greater power we employ to examine, the more light is thrown upon the fubjed:. If it had been poffible before to doubt the nature of that circle ; under this advantage of greater magnifying, it is not. The ftrudture of Rind and Bark are fo dlftindl in it, that an accu domed eye would declare at once, that it was a view of thofe two parts taken from fome very good fubjedt which he had before him : they would appear the abfolute Rind and Bark of a Shoot, not their embryo's in the Corona. On the Corona and its Clufters, (for in Nature they are never feparated,) on this complex part depends that incommunicable property of Vege- tables, that they can be produced entire from every piece. In animals, even where bounteous Nature has given the wonderful advantage of a re-produ6tion of parts, flill it is but the part which was Igft that can be fo produced. The leg of a crab being broken off, a new one grows in its place : but then it is only a leg. Nay, even in Spalanzani's great experiment of the jaw of a ^^ e "-'-'- Con ojsr^^ ,,' %h^^\ H\ )k.j\ Z'/ i? 1l Explained by the Microscope. 63; of the Newt, when that part is cut away, 'tis that part and no more that grows again : but in Vegetables the whole arifes from a part j and that from every part cut off tranfverfely, with almoft equal eafe. Thefe Clufters follow the courfe of the other portions of the Tree -, they are therefore every where: they are always capable of growing ; and their growth, even in a cutting of the fmallefl twig, cannot produce a leaf or any other part of a vegetable alone, but muft afford the whole ; for they are complete bodies, and the whole is there, waiting only for the means of extension, fufficient nourifhment. 'Tis hence in all trees Shoots are thruff forward from the Crowns and iides of Branches in Spring, and after Midfummer, the feafons when the vef- fels are mod filled ; and hence that at all feafons-^ under fufficient fhelter and defence, Branches rife from naked cuttings, under the Gardener's care. That they do not rife with equal eafe and readinefs from all kinds of trees is owing merely to the difference of conflrudion in thefe Clufters of the Corona. In thofe fpecies where that fpungy 6a The Construction of Timber fpungy matter of the wood, d. Fig. 3. is ver^ loofe and open, the cuttings grow very freely : in thole where the fame fubflance is much more compad, and prefles more upon the veffels, they grow more difficultly ; and where it is very hard', they will not in the common method grow at all. It will be worth the pra6tical Gardener's while to attend to this : for, to raife fuch trees from cuttings, there requires only to wound in many- places this interior woody fubflance, and that w-ay, to give the veflels freedom. He mud not be expeded to ufe Microfcopes to find them cut, 'tis fufficient that he be told in general twhere they are j they He deep, juft above the Pith : and when he would raife a Tree or Shrub of the harder kinds from cuttings, he is only ito" cut ir.to the piece all round, as furgeons fcarify. He will deftroy many of the parts ^ but •enough will remain to furnilL matter for fome .Shoots. Something of this truth feems to have been conceived by pradical Gardeners; fome of whom have recommended flitting, flafhing, or pricking holes in the part of a cutting or flip to be 'put into the ground. Others have decried the pradice ; Explained by the Microscope. 6^ j)ra6lice ; and, as they fay> from ill fuccefs upon the trial. Both may write truly : but they have judged too generally on a fubjedt where the matter depends upon the different ftrucfture of particulars. He that cuts or pierces a foft fpecies, where the part furrounding thefe vefTcls is loofe and open, lets in deftrudion and rotten- nefs to the whole : but he who performs the fame operation upon kinds where it is hard and too compadl, gives courfe to the natural powers and method of cncreafe. If thefe kinds be fcarified, and the others fecured by wax from the too free ingrefs of the moifture of the earth, few will fail. CHAP. IX. Of the Pith. IN the center of every young Shoot of a Tree refides the Pith : greater in fomc, and lefs in others j but prefent in all. It is placed clofe within the Corona ; the moiflening of whofe clufters, and giving moderate and regulated way E to 66 The Construction of Timber to their extenfion, is its great office : for the thing itfelf, and its deftined ufes, have been mif- taken. It is fuppofed coeval with, or primordial to all the other parts ; but it is indeed poftnatc, and comes after them in the order of time, as well as in its ufes. It is no other than a cellular fubflance, formed from the inner furface of the Corona, when the growth of the clufters of that part begins. We fee nothing of it in the Corona itfelf, tho' ever fo carefully examined j for it does not exift in that part while dormant : but as foon as a clufter leaves the circle, and its parts feparate for growth, this fpungy matter is formed within them. Exhaled air gives origin to its Blebs, while the thicknefs of the juices, cloathing the Bubble, gives it form and fub- flance. Thus is this interior fubflance formed, which has been fuppofed primoeval, and the great caufe of production, of all the refl. Its office is re- quired only while thefe clufters take their firft growth, and it adts no longer. The firft fcafon is the time of its great ufe, and it immediately after begins to decay. Thus Explained by the Microscope. 6j Thus we fee trees have parts of limited and temporary ufe. The great vefTcIs of the wood perform their office for feveral years ; but it is only at particular ftated feafons : in Spring and at Midfummer we find them in their duty, full of their proper fluid j at other times vacant and inactive ; the Pith, in the fame manner, lives and adls for the firft year ; and fcarce longer. The ftrudure of the Pith has been as little underftood as its office : figures have been pub- lidied of it, reprefenting it as formed in circles, hexagons, and polygons, with fiarry points, and double lines, and an infinitv more of varioui configuration : yet the thing is but one. To fee it truly, we muft look where it is mofl fimple. The Walnut affords it in this condition. If we fplit a Shoot of the common Walnut, of the growth of one feafon, directly down the mid- dle, we fee the central part divided acrofs into feveral cells by thin membranes, as in Plate X. Fig. I. 2. Each of thefe cells is oblong, fmalleft at the ends, and larger in the m»ddle, as Fig. i. a, and examining the fmaller part we very diftin<5lly fee two membranes forming; the two fides of E 2 the 68 The Construction of Timber the cell, and feparate from the membranes of the cells above and below, tho* they join the one and the other in the middle b. Following the courfe of this furrounding membrane round the whole of any one cell, we fee that cell in its true nature : it is an oval Bladder or Bleb, of which this membrane forms the oval. Such a one is reprefented alone at Fig. 3. The whole of the Pith is the fame with its parts j therefore the Pith of the Walnut confifts only of one range of thefe bladders, fmaller at the edges, largefl: in the middle, and laid very exactly one upon another. The Corona of the Shoot keeps them in their place fideways : they have no weight, fo they do not prefs upon one another down- ward ; and therefore they retain this form. It is only in a very few trees that the Pith is of this fimple confljudion ; but having feen it thus in one, we fliall underhand it in all. It is the quality of the Corona to throw out blad- ders of air, clofed in thin membranes ; they are large in the Walnut, and therefore each reaches acrofs the whole branch j but in other trees they are fmall ; and many of them muft be laid horizontally together to extend from fide to fide Explained by the Microscope. 69 iidc of the Shoot. In the Dog-Rofe, reprefented at Fig. 5^ we fee it takes ten or twelve circles of the Pith Blebs, to fill the vacant middle of the Branch : but ftill thefe Blebs are the fame as in the Walnut ; only that here they are fmall and round; in that large and oval. One of thcfe Blebs, feparated from thofe above, below, and on each fide of it, appears as at Fig. 6. It will be obferved that at Fig. 5. where the whole body of the Pith is reprefented together, the outline of every Bleb appears double ; and, as it were, jointed in leveral places. This is one of thofe wonders which have been reprefented in elaborate engravings : but it is the mere deception of the eye, viewing a thicknefs of the Pith in which a great many beds of the Blebs are feen together, lying over one another. There is no difference in the form of one Bleb and another ; and we have feen at Fig. 6. what one Bleb is. Its membrane is fimple, and its outline is fingle j but here the oJitlines of many Blebs are feen one over another^ and varioufly inttrfeding one the other. E 3 It 70 The Construction of Timber It has been the cuftom to view fuch a llice of the Pith as could be cut off thin with a razor ; but the moil careful way of executing this takes in many courfes of thefe Blebs. In a flice cut to one thoufandth part of an inch, by the engine here figured, a great part of this deception vaniflies, becauie very few beds of the Blebs are taken : and in one of the fifteen hundredth part of an inch, (for the inftrument will afford fuch) the whole error vanifhes. We fee the thing as it is j one fimple arrangement of cut plebs. Such a piece is reprefented at Fig. 7. With refpe6t of thofe other figures fuppofecj to cxifl in the Pith of Trees and Plants, I have fomeiimes exemplified their appearance by the flrud:ure of a piece of gauzcj which, tho* comr pofed only of ftrait lines, perpendicular and horizontal ; that is, forming fimple fquares ; yet if it be laid double, a new arrangement of lines appears 5 and if again doubled, yet another; and fo on, till, at fix tirnes doubled, the variety is in a manner endlefs. The dif- ference of figures cannot be mors between the )earances of the Pith of different trees, all 2 ni^de t - J^ITJH JPl. J 7 e s Explained by the Microscope, ji made by fimple circles, than in thefe which our- lelves have formed of limple fquares. Thus ends the examination of the feveral conflituent parts of Timber. Thefe are all : They are elTential -, for thty are found in all kinds ; and they are here reprefentcd as they have appeared, in repeated obiervations, to the Author ; to his noble Patron ; and to many aflemblies of pbilofophic friends. Nothing is enlarged, nothing altered from what the fight received in thofe feveral views : if in any part he has been yet deceived, let it not be im- puted to purpofed mifreprefentation. Nothing is feigned : and if in any thing he has erred ; Reader ! thou art a man, and pardon human fraijty.' E 4, BOOK '2 The Construction of Timber BOOK IL Of the Vessels of Trees. CHAP. I. Of the Vasa Propria Exteriora: or, The Outer Range of peculiar Vessels in Trees. THE Vafa propria, or peculiar VefTels in Trees, are not of the nature or condition of their conftituent parts, already defcribed. Thefe lafl: are eflential to the nature of a Tree, as a Tree : the others are accidental, and belong only to the fpecies. The Vegetable Strudture can exift without thefe : but it cannot without the others. They contain the particular juices on Explained by the Microscope. 73 on which the virtues, qualities, and fpecific properties of Trees depend. A Tree can grow and Hve, and give (hade without them ; but it cannot have eminent quahties. Thofe arc greateft where thefe Vafa propria are large/l or moft numerous : and where we fcarce fee thefe, we hardly tafte or fmell the other. Of thefe VeiTels there are many ranges dif- pofcd in or between the feveral parts : their fituation could not be underftood from defcrip- tion, until thofe parts were particularly known ; but now they will be traced with eafe. Of the Vafa propria there are four kinds ; and of thefe each has its allotted place, its peculiar form, its different ftrucHiure, and its feparate ufe. Some trees have them in all their parts ; others in fome of them ; and there are which fhew them not at all. Where they are not difcernlble by the eye, reference is to be had to the tafte j for if there be nothing per- ceived by that, where none appeat to the fight, it may be reafonable to give over the fearch, and conclude there arc nope. To 74 The Construction of Timber To follow the order of their arrangement in the Tree, their kinds are thefc ; i . The Vafa cxteriora, lodged between the Rind and the Bark. 2. The Vafa interiora, fituated in the Bark. 3. The Vafa intima, lodged in the Blea. 4. The Vafa peculiaria, in the Corona. Befidc thefe, there are the Sap Veffels in the Wood ; but they are common to all Trees, The firfl of thefe, the Vafa propria exteriora, have been {hewn in their place and proportion at Fig. 3. where they appear as round dark- coloured bodies, lodged between the Rind a, and the Bark i>, and entrenching upon the fub- flance of both, making their own beds half within the Bark, and half within the Rind. To know their ftrudlure we muft carefully feparate the outer Rind from the inner Bark ; and this may be done, with fome attention, in a living Branch, juft at the time of its fweliing for the Spring, or for the Midfurnmer Shoot i but much eafier by the means of maceration. When Explained by the Microscope. 75 When the Rind is perfedly feparated that way, it leaves the Vafa propria of this clafs behind it : they fcarce adhere to the inner Bark ; not at all to the Rind ', and therefore lie undif- turbed upon the piece thus ftripped. We fee them as reprefented in Plate XI. at Fig. i. they are difpoied in little packets, like cords, and do not run ftrait down the Branch ; but inter- weaving with one another, form a very pretty Icind of net. When we raife any one or more of thefe packets of Veflels, we perceive that it here and there flicks a little to the fubftance of the Bark, but no whei-e to the other vefTels : they part very freely where they pafs over one another, and will indeed fall afundcr in thofe places, if they be clipped fhort, and fhook about in a paper. When we examine a thin tranfverfe piece of one of thefe packets, we perceive that it is compofed of twelve or fifteen diftincfl vefTels, whofe Rinds feem hard, and mufl indeed be fo ; for they preferve their roundnefs notwithftanding their 76 The Construction of Timber their mutual prefTure of one another, and the preflure alfo of the Rind and Bark. A view of fuch a piece is given at Fig. 2. Laying feveral longer pieces of thefe packets before the Microfcope, we fhall, with a great power, find fome happy fragment in which we may fee the caufe and nature of the adhefion of thefe parts to the Bark. Such a view is given at Fig. 3. We fee at one end the velTels of the packet a little feparated, and in the parts a a a ■we perceive upon the fides oval depreflions, dotted as it were with pin holes ; thefe are moft probably a kind of glands, which feparate, from that general ftore of Sap with which the Bark is filled, the peculiar juices which are found in thefe vefTels. A great deal of patience, a vaft number of objeds, a good Microfcope, and a fair day are requifite for viewing the Vafa exterlora, for this purpofe ; but he who takes all thefe precautions will not be difappojnted. If fome of thefe packets be worked about with gentlenefs, the open ends will give an opportunity PI. // J^s^ :pjrojpiu1'± ejctserzoil^^ 2---" A ^'^K\>v ^>:r-. 4 EiJ^PLAlNED BY THE MiCROSCOPE. 77 opportunity of getting feme vefTels fcparate and fingle. Thefe being put into fpirit of turpen- tine, will, after a week's ftanding, become very tranfparent : and one of them, viewed with a great power, appears as at Fig. 4. divided in a very wonderful manner tranfverfely into cells : thefe are (hort, oval, and terminated by hollow valves ; and ufually, fome of them being full, and others empty, the conftrudlion is very pret- tily fhewn. We fee 2X b b fome parts of thofe pin hole glands ; and it is fingular they always have their origin at the bafe of a cell longer than the others. The brownnefs of the con- creted juice in the Oak, from which all thefe obfervations are taken, renders the cells which are filled very diftinguifhable : but there are other vefTels, with colours more diftinguifliable /lill, to be mentioned in the fucceeding chapters. CHAP. 78 The Construction of Timber CHAP. II. Of the Vasa Propria Interiora* THESE are Veflels generally of more im- portance than the preceding ; and often of more than any other part of the Tree. They are, in fuch kinds as are renowned for medicinal virtues, ufually large : they carry the milk juices in the Sumach ; and the greatefl quantity of the turpentine, as alfo the fineft and higheft flavoured, is lodged in them, in all the kinds of Pine. Their fituation is fhevvn in the Oak in Plate III. at letter d -, but tho' they are of no moderate fize in that Tree, they arc yet much larger in the Pines ; we fliould therefore feledl a Tree of that genus for the tracing them in the prefeht inftanece, if there were no other caufe of preference : but 'tis our bufinefs to fee them Explained by the Microscope. 79 them as clear and free from their juices as pof- fible, in order to underftand their ftru J^essells Tl.,4 ^ - /- 3-' -J fill ' ''•(iilllf f 4 - <5 Explained by the Microscope. 93 After this it is to be removed from the fire, and the Sticks immediately taken out with a pair of nippers 3 when they are cold, the rough wax about them is to be broken off. Both ends of each Stick are to be cut off half an inch long, and thrown away ; and the middle pieces faved, Thefe are then to be cut into fmaller lengths, fmoothed at the ends with a fine chiflel, and many of them fplit in various thicknefles. Thus are obtained preparations, not only of great ufe, but of a wonderful beauty. Many Trees this way afford handfome objefts as well as the Oak J and in fome, where the Sap VelTels are few, large, and diftind:, the fplit pieces refemble ftriped fatins, in a way fcarce to be credited. It is in fuch that the outer coats of thefe Vellels are mofl happily of all to be examined. CHAP. 94 The Construction of Timber CHAP. V. Of the Vessels of the Corona. WE have feen what are the differences of VefTels in the Vegetable Stru<5ture ; for we have already viewed ail their kinds. The Corona is the whole in miniature : it contains the embryo's of future Shoots j and therefore muft contain their Veffels, and can contain no other. We have feen that of the two parts whereof the Corona confifts, the Ring, and the Clufters, the Ring is the fame with the Bark -, it there- fore has the like Veffels. Their appearance indeed is only that of the fame objeds viewed with a lefs power : only in one point there is a manifeft Explained by the Microscope. 95 manifeft diftindlion. This is in thofe openings which a great magnifying power difcovers in thefe Veffels. Thefe are proportion ably twice as big in the Bark VefTels of the Corona, as in thofe of the grown Branches : nor is it difficult, from what has been faid of their ufe, to guefs the reafon. Thefe VelTels are reprefented at Plate XV. Fig. i. As the VeiTels of the Circle or Ring of the Corona diifer in nothing elTential from thofe of tlie Bark ; neither do the VelTels of the Clufters differ more from thofe of the feveral parts of the grown Tree, of which they are the embryo's. It is often poflible (I cannot indeed fay it is always eaiy) to diftinguifh the Vafa intima in the outer and inner ends of each Clufter 5 among the Veffels of the Blea. They,^ a^ well as the Blea Veflels, are very difficultly viewed with any diftindlnefs in this compact and crowded con- dition ; wherein they ftand in the Clufter : but what difference I have been able to fee, in thefe lelfer Blea VelTels, is, that they have fe werbut larger mouths than thofe in the Blea of grown Shoots ; and that there is an utter want of the fpungy interflitial matter which in that ftate keeps them feparate 96 The Construction of Timber' feparate and at a diftance. That the Vafa intlmai the proper obje6l of enquiry here, have thinner coats, and are not fo perfectly cylindric. In the central part of every Clufter v^^e muft exped; to find thofe vaft Sap Veflels which feed the whole interior part of the Tree ; nor are we difappointed : they are indeed yet larger in proportion here than we find them in the grown Branches ; for 'tis here they have their greateft ■ufe : 'tis thefe alone that can fupply the Shoot in its firft pufhing out from the Branch. It is to grow before it has communication with the outer air ; and 'tis by thefe Veflels, which here are always full, tho' in other parts they arc fo only at particular feafons, that the growth of an angle of the Corona is to be fupported and iupplied in its egrefs into a Branch. BOOK 1"EjSSelij/S of tjte Coitojv^± '^ t "^ PI -'6 or t/fje^ C<7?'tj7Zct ^ / aJw /t n-te ?/? a ah m e Qn^oji a ' Ar/? L^e^f^//^f oftA/' 'Co/^rnta Explained by the Microscope. 97 BOOK IIL Of the En CREASE by Growth. CHAP. I. Of the Growth of Branches. TO know the parts of the Vegetable Con- flrudlion, unlefs we have alfo from that knowledge learned fomething of their ufes, were a vain and idle boaft. The encreafe of the Tree, the new and multiplied life that it receives from the growth of Branches, each capable of be- coming an entire and feparate Tree by only flicking it in the ground 3 is a matter of the firft moment. The ceconomy and encreafe lie G here ; 98 The Construction of Timber here ; and the ufes of men are fupplied as well thus, as from feeds; and with the advantage of more expedition. Since it is from an angle or part of the Corona the Branch naturally ariles, 'tis in this place we may mod naturally and ufefully trace it. There have been miftakes about the nature and method of the growth of parts in Plants, as well as in relation to thofe parts themfelves : but 'tis not the purpofe here to point out the errors of others, but plainly to enquire the way to truth. It has been thought, nay it has been affirmed under the fancflion of very reputable names, that the Pith is the firft part in all growth, and that the others form themfelves about to cloath it. Experiments have (hewn 'tis otherwife ; and the way to certainty in this enquiry is fo plain, that 'tis impoffible any one dhpofed to obfervation can miftake it. The Pith is fo far from being the original or firft formed part, fo far from giving origin to theTeft, that they are always formed or puflied forth without it. The Pith begins to grow after the Branch has fhot to fome length, and ceafes Explained by the Microscope. 99 ceafes to be of ufe after a few months : nay in the end lofes again its accidental being, the Branch remaining perfectly found and healthy without it. Any Clufter in any part of the Corona, pro- truding itfelf onward and outward in the grow- ing feafon, carries a part of the Circle out with it. This protrufion is naturally made in the bofom of a leaf, becaufe the Bark and other parts are there weaker and moifter. The Clufler itfelf is a pcrfedl piece of the Wood and Blea j and the Bark which follows it out in its progrefs, per- fedly cloaths it. Thus is the firft protrufion of the Shoot made : but all this while there is no Pith. There was none originally in the Cluiler of the Corona, and all things yet appear unaltered in it ; only for their covering. The continuation. of growth is made by the extenfion of all the parts obliquely upwards : in the courfe of this- extenfion they hollow themfelves into a kind of cylinder, the form of the future Branch : and by this difpofition a fmall vacancy is made in their center. This enlarges as they encreafe ; and £s it enlarges it becomes filled by the exfudation of thofe little bladders before-men- G 2 tioned : 100 The Construction of Timber tiontd ; which remain and conflitute the Pith j fed iiom the inner coat of the wood, which already begins to form itfelf into a new Corona; by its eladicity preferving, and enlarging that cavity it fills. To follow this enquiry fuccefsfully, fplit a young Shoot of the Red Dog-Wood, or of the common Dog- Wood of our hedges, early in Spring. If the fiiTure he continued diredly diro' the two oppofite Buds in any part, there will be leen an angle of the Corona forcing itfelf out on each fide, in order to make a pair cf oppofite Branches. Each protruding angle forces its way thro' the foft young Wood, not by tearing its VeiTels, but gradually infinuating itfelf between them ; and nothing can be plainer than that it is an entire Clufter which is thus thruft forward to become a Branch ; and that it leaves a thick line of the Circle or Ring of the Corona behind it. This is very happily viiible in the Red Dog- Wood of America; becaufe the Circle of the Corona is at that feafon very green, and perfedly didinguifhed from the Wood, which is of a v/hitilh hue, and from the Pith, which is of a pale brown. The Bud, pufhing onward.. Explained by the Microscope. ioi onward, leaves a kind of vacancy behind it, or between its.afcending bale and the hne of the Corona : thro' this vacant fpace pafs a multitude of veflels, which fupply the afcending Bud with a great deal of nourifliment from the hne of the Corona, which is left behind it. Here feems the great ufe of this line of the Corona in the ceconomy of Nature : and in the path of knowledge it fervcs to elUblKh, beyond doubt, the True Hiftory of the formation of that fappofed original part, the Pith. The Clufter of the Corona, which is to be a Branch, communicates with every part ol the parent Treej except its Pith ; but all communication with that is ftopped by this circle : nor can there be any intercourfe of juices between their Vedels and its Blebs. We fee in tlic examination of the Clufter that it his no Pith of its ov/n : we fee by this line of the Corona it can have no communication with the Pith of the Tree ; and 'tis not only impoffible that this fn:5gular fub- flance fliould pierce that Ring, and enter the Clufter, but our eyes fliew a fpace, a vacancy, between them : a part of the Shoot, wherein there is no Pith , and in its place a courfe of G 3 Sap- i02 The (Construction of Timber Sap-Vefiels ; things perfedly ciifl:ln(^ from it, in nature, form, and difpofition. This fpace, tho' it be proportionably greateft in the very young Bud, yet it remains long vifible after the Branch is grown j nay, and in fome kinds, does at length obtain a kind of coarfe Pith for itfelf. At Plate XVI. Fig. i. is fliewn a piece of g young Shoot of Dog- Wood, fplit thro' the two oppohte Buds, to Ihew their nature. The part a is the remaining line of the Corona ; b is the fpace left by the aicending Bud ; and c are the Vcilels pervading it. If now we take a thicker piece of the fame Shrub, and inflead of fplitting it thro' two Buds we cany tl>e knife thro' the ftumps of two Branches, formed by two fuch Buds in fome preceding feafon, v^e find the veftiges of every part remain. Such a piece is reprefented at jPlate XVI. V\z. 2. Here we fee the line of the Corona (letter a) flill remain, but not fup- piied vv'ith any new Cluder : and hence we may Jeam that a fecond Branch can never rife from ^be faine fpot, altho' the firil fhould perifli by any accident. GrOWTS of BlLAJ^CHE S -^/./^. Explained by the Microscope. 103 accident. At h the fpace dill remains ; and its Veflels c run thro' it : but as we carry our eye along the afcending Shoot, we fee at ^ a Pith in all refpeds the fame with that in the center of the parent Branch. This Pith of the Shoot is not continued from the Pith of the Branch, as has been fuppofed j for they are not, nor ever were, continuous: there is, there always has been from the beginning, a fpace between them : the fpace exifted even before the Pith of the Shoot was formed. This Pith therefore was neither derived from the parent Tree, nor original in the Shoots but is a mere temporary and perifhable production, exfudated from the Shoot itfelf, and deftined to ferve its prefent purpofes, and then to periih. Let not the newnefs of this opinion make any one pa-jfe to receive it ! Had we never had new opinions, old errors would have been im- mortal : but happily here v/e may refer not only to the Reafon, but the Eyes ! The fhrub is before every one; a pen-knife makes the divifion ; and fcarce a common reading-glafs is neceifary to obferve it. G 4 Altho' 104 '^K^ Construction of Timber . Altho' in this Shrub the vacant fpace left by the afcending Clufter remains empty, it has been obferved that there are fome in which that very fpace itfelf becomes, after a time, filled with a fort of Pith. The Dog-Rofe or Wild-Briar of our hedges gives an indance; and it is always happieft in thefe purfuits when the needful ob- jeds are the mofl familiar. A Branch of this, with a Shoot rifing from it, is reprefented at Fig. 3. In this the line of the Corona left behind is very diftindly vifible at /2 J and the Pith of the Shoot at /; ; termi- nating, as is always the cafe, convexly towards the Branch. Thefe two parts are very diftindlly known by their green and brown colour ; and in the original vacancy at c there is found a mafs of a kind of Pi:h, very coarfe in com- parifon of that either in the Branch or in the Shoot J and perfecflly difl:in<5t from both, com- municating with neither. In the Virgin'a Creeper, Fig. 4. the very Pith of the Stem is not continuous -, but ends ob- tufely Explained by the Microscope. 105 tufely upward, and obtufely downward, as in the Branch. And in our own Vine it is not only difcontinuous, but in the mod perfect ftate of the Tree is intercepted, as at Fig. 5, CHAP. II. Of the Prolongation of the Shoot. r^j~^ H E Prolongation of a Shoot already A formed, is plainly a matter of more fun- pie circumftance than the produd:ion of a new one : and here one would. fuppofe the Pith, like the other parts, might be found continuous : but Nature, always confiftent with herfelf, the God of Nature adting every where in the fame amazing manner ! confirms the dodtrine of the feparate formation of that part, in the Shoots, by its appearance, lefs exped:ed here. — Be it fuffered, Lord ! to ufe thy name in honouring thy- works. The 3o6 The Construction of Timber The Prolongation of the Shoot in Trees is not a thing conftantly and regularly going on ; it has its feafbns and its times ; and takes its courfe more rapidly at fome, more ilowly at others : and there are Tome when it nearly ceafes. Let us follow its progrefs thro' a year ; for the fame is every year repeated : and tho' in various degrees of greater and of lefs, of fwifter and of flower ; it is the fame in all. In Oiflober, if we feleit a Shoot of the Afli- Maple, a quick growing Tree, we fee its end terminated by a cone, compofed of films. Here the growth of the paR feafon has flopped. This cone is what we call a Bud j and thro' thefe films, at the enluing Spring, the Pro- longation of the Shoot is to be continued. Such a piece is reprefented at Plate WIL Fig, I. In this flate it remains thro' Winter: the cold having clofed thofe pores thro' which the Root ufed to draw in the greater part of its nourifhment. Explained by the Microscope. 107 nourilliment. When the warmth of Spring returns, the Roots fwell, thefe pores open ; thofe vaft cifterns the Sap Vefiels of the Wood become filled, and every thing is nouriHied and begins to grow : the Shoot extends itfelf thro' its films, and feems a young Branch grow- ing from or upon the old one. If we let it take its deftined encreale till May, 'twill then be in a condition to examine as to the nature of its growth, and the condition of its parts. Such a piece is (hewn at Fig. 2. entire ; and at Fig. 3. fplit regularly open, with the fiffure carried down into the Shoot of the former feafon. What we fee in it while whole is, that the top has been well covered with films -, and there is an appear- ance as if the growth had come to an entire Hop there : but in the fplit Shoot we fee 'tis otherwife ; there is a fwelling at what was the top, a a ', but the brown Bark and the white Wood, after thickening in their paufe, are con- tinued : they afcend juft as the Clufler from the Branch, and leave like that a little fpace behind them, e. In the new growth all therefore is continuous except the Pith : the Vefiels are only lengthened ; but the Pith has ceafed. It comes %o an abfolute termination, in an obtufe form, as io8 The Construction of Timber as in the other iniiances ; and after a fpace is left. Fig. 3. 6 i>f a new Pith is generated in the afcending Shoot, the fame in texture, form, and colour with that below: but, as has been juft fliewn in the other inftances, perfectly difunited from it. The. new Pith therefore is not a con- tinued growth of the old ; but a fubftance ; produced, as that had been, from the other parts. In this Maple the Pith has kept its cylindric form throughout, and not thickened at the end with the fwelling of the top of the Shoot. In the Pine, Fig. 4. where that fwelling is greater, as it only affedts the exterior parts, a greater fpace is left within than in the former, as at Fig. 5. but if we fplit fuch a Shoot, we find 'tis not a vacancy that is left ; the Pith fills the larger hollow as fafl; as it is formed ; for 'tis only at the exteniion in length that its courfe ceafes. In the Plane Tree, where the difpofition of the Pith is more irregular than in many other kinds, wherever the cavity extends, as at Fig. 6. and 7, a. the Pith always goe3 with it ; but frill at the place where the Shoot of one feafon ceafed ; and Qll O WTH ,^r:^R OM TSE Cjl OWJST ^^ ■ '7- Explained by the Microscope. 109 and that of another begins, there is a fpace between the Pith of the former, and that of the latter Shoot : b. And even in the Turpentine Tree, Fig. 8. where this fpace is lefs than in any other which has come under my obferva- tion, ftill it is a fpace, as at Fig. 9. a. The Pith of the preceding Shoot ends in the ufual obtufe manner, where the beginning of that of the young Shoot, altho' diflind:, is yet irregular. BOOK no The Construction OF TiMiSER BOOK IV. Of the difterent Difpofition of the Parts in various Trees. C H A P. I. Of Differences in the Rind. TH E flrength of Trees depends upon the conftitution of their eilential parts ; their qualities principally upon their feve- ral added VeiTels. The elTential parts ; the Rind, Bark, Blea, Wood, Corona, and Pith, are found in all Trees ; tho' differently con- Uruded and difpofed : but the vafcular parts, of this additional kind, are not only fmall and inconfiderable in many, but in fome are entirely wanting ; Explained by the Microscope. hi wanting : nor is it ftrange ; for every Tree is not deligned to be medicinal. The general nature and ufual difpofition of thefe parts has been Ihewn in one inftance, the Oak ; in which they are all prefent, and where they lie in their mofl regular form : but in the variety of Trees which God has given for dif- ferent purpofes, there are fo many variations from the general order of difpolition and mag- nitude, that it is pleafant, in the light of curiofity, to examine them ; but there are alfo higher purpofes to be anfwered by fuch examination. Since it is to the conftruition of that part we call the Wood that Timber owes its ftrength ; and to the lize and contents of the Vafa propria all Trees owe their powers and virtues j an eye, thus accuftomed to the vifible differences, will guefs, almoft to a certainty, what ftrange Trees are worthy notice, as to durability ; and what promife cures for ficknefs. To lead to this diftindive method of viewing them, itmaybeproperfirfttofeledtoneoftheleaft complex of Trees or Shrubs ; the fimpleft in its flrudure : 112 • The Construction of Timber ftrudlure : lince in fuch a one Nature will lay open many things in the orderin,.; of the parts, which are hid in thofe of a more complicated texture. For this purpofe, as one of the fimpleft of Shrubs, and one readieft at hand every where, the Dog-Rofe may be felecfted : and there will he found in it, when examined frefli cut, and in the growing feafon, a diftindiion of colour in the feveral parts, which marks their outlines: very happily. If a piece of Dog-Rofe be chofen which has finillied the growth of one feafon ; and has juft' begun that of another, (for in this quick grow- ing Bu(h a Shoot acquires in a fhort time fome confiderable thicknefs) a fedion taken from this, of about the two hundredth part of an inch in thicknefs, will exhibit the parts with wonderful clearnefs. Where colour is ufeful, this degree of thicknefs anfwers better than thofe fhavings which carry but a thoufandth part ot an inch. A quarter. EXPLAINED BY THE MiCROSCOPE. 113 A quarter, cut from fuch a fedion, and laid before the fixth glafs of the Microfcope, appears as at Plate XVIII. We are to obferve firft, the Rind, ^, which is, in this Shrub, very thick, and flands perfe6lly diftinguifhed in fuch a perpendicular view from the Bark, by its colour : it is a narrow line of white, with fmall dots, which are the Vafa exteriora in it j b. Within this we fee a very broad circle, c ; which is the Bark, vQvy thick in this Shrub, and of a lively green. Thefe parts can never appear in any indance more' diflincft. A litde way within the inner line of the Rind, lodged in the fubftance of the Bark, appear the Vafa exteriora : thefe are of fo llrong a green, that their colour diflinguifhes them from the Bark as much as their form -, d. Within the fubftance of the Bark alfo, but toward its inner part, and very near the Wood, lies the Blea, ^, perhaps better to be underflood in this quick growing Shrub, taken at this feafon, than in any other kind. We fee it, ill mofl: inftances, a pale continuous line be- H twficn 114 Tke Construction of Timber tween the Bark and Wood ; and fuch it will beconrie, after a time, in this : but 'tis now in the flate of its formation ; and appears in feveral convex pieces palpably taking their origin from the Wood ; and as yet difunited from one another. Its colour is a pale olive, and its parts are very diftincfl. It is evidently now Wood, yet tender and but half formed, forcing its way into the Bark, which it will thruft out to the very edge hereafter. The regular green line of Bark, which feparates this Blca from the Wood, broad as it now appears, will in half a year more be nothing but that llender line which feparates and marks the growths of the feveral feafons. Within this lall: mentioned green line we fee the Wood of the Dog-Rofe, J^: even that is as yet compofed of unconnedled parts : and by this view of Wood in its infant flate, and by no ether, can we truly know what it is. It is now a diftind: fubftance, in form of feveral ellipfes, of a firm fl:rud:ure, and pale colour. Imme- diately within the bottoms of thefe ellipfes we fee the embryo Corona, g, confifling of a pale convex body, adapted to the ends of thefe 5 ellipfes. DoGr-ROjSE -T/./o: ^e .,--- S" 2^^M^ :^m' _h. Explained by the Microscope. 115 ellipfes, and formed by a feparaticn of the two membranes of their parietes, or fides. With what pleafure will the curious eye, having once acquainted itfelf with all thefe parts in their diflind: and infant ftate, purfue them in other inftances; where, in their adult condition, they have united themfelves for flrength one with another -, and often loft even the appearance of their original conftru5:ion ! The Pith in the Dog-Rofe is alfo a very beautiful objed:. It has, in a flice of this thicknefs, the appearance of ftarry forms, with oval rays : but this illufion vanifhes on cutting a thinner piece. When one is viewed of a thoufandth part of an inch they appear only iimple Blebs. H 2 CHAP, ii6 The Construction of Timber CHAP. II. Of Differences in the Bark. / I ^ H E Rind of Trees, being no more than A an out-cail: of the Bark, is of little importance to them ; and we find in it very little variation : but in refped: of the Bark it is much otheru^ife. This is a very eflentlal part in the Tree ; the grow^th depending, in a great meafure, upon it ; and the qualities : and we find it accordingly very different, in fubflance, quan- tity, and nature, in various kinds. It is originally the outer membrane, covering the Lobes of the Seed. Even there it may be feen, juft as in the Branch of a Tree, in form of a kind of fpunge ; compofed of flatted blad- ders. In the fucceeding growth, the outer ranges Explained by the Microscope. 117 rano-es of thefe bladders, drying, become what we call the Rind •, for that part has no exigence in the feed ftate : it is formed by the operation of the air ; it is ftretched by the fwelling of the Woods and it is caft off once in a feafon, as fnakes caft their fkins : but not entire, only in fragments. Mean time the Bark re- mains, covering the more fubftantial parts, the Blea, the Wood, and the reft, and feeding them by a continual fupply of nourishment from its fpungy fubftance; always fupplied with water : this it draws up frefh as faft as it is drained off, and continually fupplies every fubjacent part. It proteds all from external inj uries alfo ; and defends them from the effeds of cold. For thefe purpofes it is varioufly difpofed in different Trees. In the hardy and flow growing, as the Oak and Chefnut, it is thin : in the quick growing, as Willow, Poplar, and the like, it is thick : and, what is more worthy yet of regard, is, that altho' it be laid fmoothly and in an even line over the Blea in moft Trees, yet in fome its inner verge is radiated. H 3 Thsr€ ii8 The Construction OF Timber . There are fome Trees, and a great many herbaceous Plants, in which this part is con- tinued inward, in form of rays, thro' the Blea, into the Wood ; and feems to form fo many green wedges, fplitting as it were the fubflance of both thofe parts. It would be difficult to conceive how this were done, but that we have feen in the Dog-Rofe thofe more folid parts are not originally compad; ; but compofed of fepa- rate pieces : between thefe the rays of the Bark infmuate themfelves while they are open, and keep their places, tho' in a ftiialler compafs, always aftervi'ards. The Sorbus Legitima, or true Service Tree, affords a very ftrong inllance of this : a piece of a tranfverfe fedion of this Tree is given at Plate XIX. This was cut from a Shoot in its fourth feafon : we fee plainly at the lines of fepa- ration, a a a, the growths of three perfed feafons : at if we fee the ad of growin^^ in a fourth. The Wood is here, as in the Dog-Rofe, thruit forward and outward into the Bark -, aad that not in a continuous fubflance, as at ^j but ^onBzrs LEaiTZAi^ jpr 1^ ^s'^ f '¥: \> d -a Explained by the Microscope. 119 but in detached bodies, They were fegments of ellipfes in the Dog-Rofe ; here they are cones. The brown Rind c terminates their fummits in a regular circle ; hut the Bark d infinuatcs itfelf deeply among them, filling up all the fpace between cone and cone, to their very bafes j and thence continuing itfelf, tho' in a thinner line, thro' every feafon's erowth of the V/ood, down to the very Pith. This marks out palpably, by its courfe, the feveral parts which once were cones of Blea j as the exterior, yet retaining the fame form of cones, are the true Blea of the Sorhus now : tho' in the courfe of growth their taper ends have fpread to the fame breadth with their bafes. Here therefore, as in the Dog-Rofe, and fome other inflances, the Blea is always a dii^rontinuous fubilance ; tho' in the generality of Trees it is one foft, but entire ring. The ufe of this conftruftion in the oeconomy of Nature is not difficult to be underftood : an objedl familiar to me, in infancy, firfl: threw it upon my mind. In the park of Sir Francis St. John, at Thorp, near Peterborough, ftood an old Service Tree, perfedlly divefted of its H 4 Bark, I20 The Construction of Timber Bark, yet growing and full of vigour. I remem- ber a thoufand times climbing it when a boy, and to have heard wifer perfons fpeak of it with wonder; that a Tree thus naked could live. I did not, even at a later time, underftand how it could be, till, taking a cutting from the garden of her Royal Highnefs, this ftrudure prefented itfelf to me. The coat of Bark could be fpared, becaufe there were rays of the fame fubllance within ; which anfwered the purpofe. Purfuing this fubjedl I have alfo found that the Ciflus Laurifolia, which has the fame conftrudlion of rays from the Bark, lives very well when peeled ; and 'tis familiar that the Plane will do fo. In that Tree alfo we fee the fame conformation ; and muft no longer wonder at the fame effecS:. There are many other Trees which have fome- what of this quality ; and in examining them I have found they have all fome degree alfo of this conftrudlion ; and that, (fo far as can be judged) a degree juft anfwering to their more than ufual quality of life. Tliat Leaves and Branches fhould be pro- duced from a hollow Tiee, vvhofe Wood had periflied. Explained by the Microscope. 121 periflicd, tho' the Bark was entire, ceuld not appear wonderful to thofe who knew the nou- riihment was from the Bark j but that a Tree could live whofe Bark was gone, muft feem, till this was knov/n, almofr a miracle. C FI A P. III. Of Particularities in the Blea. H E conflrudion of the Blea has been explained in its place : but its difpoiition, and the arrangement of its parts, as they are various in different Trees, become now the ob- je(ft of enquiry. The variations of Nature, in this cafe, are endlefs ; and tiiere are fcarce two genera wherein this and the other parts do not differ, more or lefs, either in their quantity, colour, difpofition, or arrangement. From the great number of kinds which have palTed under 3 • my 122 The Construction of Timber my eye on the prefent occafion, I fhall feledl thofe where the differences or particularities are moft confiderable ; and be happy in pointing out to the attentive Readcir what Trees, fo far as this experience leads me, will beft entertain his eye, and lead his thoughts to more enquiry. I. Of the plain Difpofition of the Blea in the Liriodendron Liliiferum. When we would fee the Blea in its plain, moil: natural, and moft firaple flate, that Tulip Tree which Botanical writers call Liriodendron Liliiferum affords a very fair occafion. A piece of this is reprefented at Plate XX. Here the two Barks, a by are very dlflind: j the outer of a deep, the other of a paler brown : and between thefe and the white flefh d is placed at <: a plain and even circle of the Blea. Its pale brown colour keeps it perfecflly diftind from the Bark -, and its ftrong inner margin as plainly feparates it from the Wood. This is the pure and perfed: fcate of the Blea : and were LiRIODEJKWROJSr LtZjIIFERXtjh^: TL.^^ s* .'S ^'l\^. •-^. f N \ a Explained by the Microscope. 123 were it for the condition of this part alone the Tree would demand a place here : but it has been feledted for more particularities. Nature is pregnant with wonder and delight ; and it has been the care, on thefe occafions, to chufe, among the number of thofe where the main object is equally perfecfl, fuch kinds as afford therewith moft delight or mod: inflrudion, in the other parts. In this the Vafa interiora, e, are very beautifully placed juft within the inner verge of the Bark : their oblong form is lin- gular ; and the more fo, as it is lefs regular and exad; than in mcfl cafes. The delicacy of the Wood, Jl and the arrangement of the Sap- Veflels, gy in regular rays, are alfo worthy note ; and much more their regular diminution in fize as they approach the Pith, ^. 'Tis thus in all Trees, at a certain growth j but fcarce in any is fo well fecn, or takes place in the Shoot fo early. It has been obferved, in treating of the Corona, that the ring or circle of that part wherein the clufters of veffels are enclofed is of the nature of the Bark *. this Tree gives a plain proof of it at /. II., Of 124 '^HE Construction of Timber II. Of the warped Difpoiition of the Blea in the Nerium Oleander. The Blea of Trees admits of variations frofn that plain and ordinary ilate wherein we have reprefented it before, both us to its difpoHtion and conftrud-ion : in feme Trees one of thefe differences takes place ; in others both. The form of the Shoots in the Oleander is not per- fectly round, n ; and to this the Blea, as well as the other conftituent parts, conforms itfelf. (See Plate XXI.) In fhape it is not a circle, as in the Tulip Tree, but a f/voln cllipfis, fmalier at the ends, and rifmg on each part toward an angle in the middle ; and all tiiis vv^ith ?reat regularity, b b. Its texture is coarfc, r, and its colour is a pale brown. Tlie parts of which it is compofed are the fame as in all otlier Trees ; for one conflrudion goes through all : but they are in this larger, in their cavities, as well as thicker in their fides, than in others. The warped date of the line this Blea forms round the Wood, r.nd tlie regular greatnefb' of its parts, mofl JSrERTZ::M- OLEudJSTJDEIi Ic Fl.'Z/ . iT ^r ^ ■^, Ix £ Explained by the Microscope. 125 moil: claim our attention : but the objed: being before us, it were bllndnefs not to remark alfo, that the Wood is dehcately vafcular, d -, that the Hne which is to mark the growth of another feafon is thicker than ufual, e ; that the circle of the Corona is palpably of the fame colour and fubftance of the Bark, /, and that its clufters are thrown together more than ufual on the inner lide, g ; that the Pith is remarkably large, /j ; and that the Vafa exteriora, /", and interiora, k, (hew themfelves with a diilind:nefs very pleadng. There are two rings of the interiora very large and fair, and a perfe6t line of the exteriora, at the very verge of the Rind. What juice thefe laft contain it has not been in my power to determine 3 the former have a milky acrid matter in great abundance. III. Of the undulated Courfe of the Blea ill the Nerium Zeylanicuai. Purfuing the conflrudion of the Oleander in another fpecies we fee by what gradations Nature brings about her changes. The Blea in the 126 The Construction of Timber the Nerium Oleander was warped ; here it is undulated : there it ran out into four obtufe angles j here it forms a multitude ; a continued feries of them : in this, as in the former in- ftance, conforming itfelf to the fhape of the young Shoot ; which in the Ceylon Oleander is neither perfedly round or elliptic, but all the way raifed in an uneven line, or in a kind of ridges and furrows. In the lirudure of this Blea we find a yet more confiderabie difference : it is a broad line of a pale whitifh fubftance, formed of velTels with coats fo remarkably thick, that Nature furniflies no inftance equal to it; (fee Plate XXII. a a.) and the fpungy matter which fills their interflices is in like manner prefTed dole and compadl. The colours aUb, in a frefh cut piece, afford a very good opportunity oF marking all the conflituent parts in this Shrub to a nicety ; and I hope it will therefore bec®me familiar in the collecftions of the curious. The Rind is thicker than in moft things, If ; and the Bark, c, of a very delicate texture : the Vafa exteriora, ^, are very numerous, tho' not fo large as in many others i ihclv quantity making amends for their v^-ant of fize. Their difpofition feems but irregular; yet :PL^2i. Neriuim ZEYXj.'Usricn^i^ d -1 b Explained by the Microscope. 127 yet a careful eye will count two ranges of them. The Wood, e, has fewer Sap-VeiTels than ufual ; and, what is much more ftrange, they are not perfedlly round, f: the undulated outline of all the conftituent parts perhaps prefles upon them. The Pith, ^, is immenfe, and the Corona, /6, fmall: but Nature, confident with herfelf, has given to the clufters of that undulated Ring the fame difpoiition within the line, as in the common Oleander. IV. Of the difForm Blea of the Ephedra Distich a. We have in this Shrub an inftance of the fport- ings, as it were, of Nature, in the Blea j per- fe<£lly fingular. It is coniiderable in quantity, a; it furrounds the Wood in that kind of undulated line mentioned in the preceding inftance ; and to a corredl obferver it appears very diftindly to be of different textures in its different parts : a line of Veffels nearefl the Wood, and a mere mafs of confufion behind it, toward the Birk. This will not be difficultly underftood by thofe who 128 The Construction of Timbei^ who have fiift acquainted themlelves with the compofitioii of the part. We have feen it is conftrucfted of vcfTels and an interflitial fpunge. All that is fingular here is that the fpunge ufually placed between velfel and veffel is kept feparatc, and thrown behind, A fedtion of the Ephedra is given ^n Plate XXIII. and thefe two parts of the Blea are feen at <: i. ^ 2. But the Ephedra gives us much more matter of delight and wonder. With refped: to its Rind and Bark, a b \ and the dilpofition of the Vafa pro- pria interiora, fy (for exteriora it has none :) they differ not from what is the ufual courfe : but the Wood, J, which is delicately con- ftrudled, fliews the diminution of Sap-Veffels toward the center very diftindily : we even lofe them near the inner part of the laft grown circle of the feafons. But befide this, that beautiful advance of the Wood toward another of thofe circles j that which charmed us in the Dog-Rofe, raifes raptures here. We fee dif- tindtly at e the pufliing for a third circle of Wood ; and here knov/ how it is form.ed. The parietes of thefe fruftrums of cones, which in this objedl anfwer to the ellipfes of Wood in the Dog-Rofe, are extended in growth before ths EPHEDRA Dl^TZCH^ FL23. \ Z £ - d ^ c- / . c . 2. ■ Explained by the Microscope. 129 the matter of the Wood is formed to fill them. It Is palpable, in a good view of this kind, that they are well marked, but perfe6lly empty. The Corona is very beautifully hollowed ; and in the Pith are palpable VelTels. This is the firft occafion that has offered of naming them ; but we fhall fee them in fome other inftances. They are the Vafa intima, fo flrangely difpofed ; this their flrud:ure fliews, and the firmnefs of their contents. Thefe pierce the Pith in a longitudinal direction ; or more probably they are primordial in the fl:ru(5lure of the Plants and the Pith is formed around them. c II A r*. 130 The Construction of Timber CHAP. IV. Of Particularities in the Wo 00. I. Of its fimple Strudlure in the Com- mon Dog-Wood. ANEW thicknefs of Wood is given to a Shoot at every Spring and Midfummer ; diftingulfhed by a circle, marking the place where the former ended. The iifual appear- ance of a fedion in this part is that of a mul- titude of rays, proceeding from the Blea toward the Pith ; cut in many places by concentric circles ; at different diftances. But the number of parts confounds the eye -, and to know what the Wood is, we are to feek it in fome fimple ftate. No in/lance affords this better than a fedion Explained by the Microscope. 131 fedlion of a young Shoot of the common Dog- Wood. If we felect one from a Branch th^t has had but one feafon for its growth, the appearance it gives before the Mierofcope is tiiat figured at Plate XXIV". When we have cad an eye upon the Rind and Bark, and the broad circle of the Blea, a b c, we fee the great, plain, and nobk ftrudure of the Wood at d; :and find at e^ what we had before feen in the .Dog-Rofe ; that the Corona, howfoever after- wards it be filled, takes its original from the parietes or fides of thofe obtufe broad cones which here are what the ellipfes are in that other Shrub. And it is palpable that here in the Corona, jufl as in the protrufion for a fecond ifeafon's Wood, thefe parietes are the firfl part -that -grow. They form the (pace which there is to be filled with the matter of the Wood ; and here, by amuch more complex and won- derful fubftance. The Wood is in this inllancc the mod plain and fimple thing imaginable ^ and its parts being naturally large, and not prefTcd together as in the harder kinds, can be viewed diflindjy, and eafily underftood. We, now fee that the Wood, I 2 which 132 The Construction of Timber which in old hard Trees we look on as one mafs, is formed of cones, with bafes tending outward, and each cone perfectly inclofed in a thick fliell, of a matter more compad: by far than the intermediate fubftance. Within thefc cones run muhitudes of rays, all like the parietes of the cones, converging inward -, and in reality each two of them forming a leffer cone, within the larger. Within this lelTer cone, between tliefe rays, is depofited the fubftance of the Wood, pierced with innumerable holes j or, in a more juft: way of fpeaking, giving place to a multitude of Veffels. Thefe are the Sap-Veffels. The intermediate fubftance is the moft compad: part of the Tree : and this is always the real ftrucfture of that part ; however it may in various inftances feem to fliew a wonderful variety. The Pith of the Dog- Wood, /, is, as the reft, the fimpleft we can look upon ; a mere col- ledion of hollow cells crowding and preffing upon one another. If this conftrudion of the Wood, which is fo eafily under ft ood in the prefent inftance, be always held in mind, as we examine others, the DoawooD :pt,Q^4 "^ ' d 'a Explained by the Microscope. 133 the fecrets of the compofition will be laid open to us with lefs pain. IL Of the Length of the Cones in the Acacia Decidua. A Tree which affords an indance of equal fimplicity with the Dog-Wood, but in a new form, is the Acacia Decidua : a fe(5lion of which is given at Plate XXV. yet the fmallncfs, or, if it may be better underflood, the delicacy of its parts renders it lefs obvious ; and leads us, as by a fingle ftep, from that fimple kind to the appearance of the more complex. The Rind in this Acacia is very thin ; the Bark is alfo thin ; a b : and in the Blea, which holds fome breadth at r, are difpofed Veflels fo very much refembling the interiora of other Trees, that we {hould fuppofe them of the fame nature, if we did not firft fee them in a place where the intima alone can (land ; and if the firmnefs of the matter with which they are filled did not confirm it : but beyond all, their own flrudure : I 3 "for 134 T'he Construction of Timber for they are fimple VefTcls j their fides are not vafcular. The M^ood, which lies nearly within thefe, coniifts of very long and narrow cones. The parietes of thefe are extremely diftind:, tho* fine } and the whole Wood is pierced with Sap-' VtiTcls fo large, that its own vafcalar ftru(fture» which is indeed in all Wood very - delicate, affords the idea of a compact and folid fbbfiance. Nature, in this inftance, giving all to the Wood„ contrads the Pith, and half annihilates the Corona : 'tis very fingular : but {[ill the parts of that circle are to be feen in thefe young bhoots of the Acacia Decldua : and in thofe of more ftanding they become as large as ufual. Why and to what end Nature, where nothing is done in vain, gives this exuberance of Wood to this, and the fcanty flore of it to Dog- Wood,, are queftions for a very high philofophy. III. Of dc^cx^ Decivz^.^ W ' Ft. ^^■ ^f S -~~ e Explained by the Microscope. 135 III. Of the tliick Parietes of the RoBiNiA Caragna. He who will join with me to purfue the lafl: named plan ; and try if it may be found why, in the Robinia now before us, the fides of thofe cafes wherein the Wood is held are remarkably thick, or, if we may ufe fo ftrange a word, fo coarfe ; will perhaps open the way to a knowledge of the nature of Trees, which, tho* propofed more than two thoufand years ago by Theophraftus, has pafied thro' the hands of all his fucceffors untouched, fo far as their writings have informed us ; therefore, at leaft, not happily followed. The appearance of a fedion of this Tree Is given in Plate XXVI. In the Rind and Bark, a bi nothing is particular. The Blea is very firm, compa^ft, and delicate. In the Wood there are, as it were, fhadows of circles ; nothing real : but ftill we find the Sap-Vefiels difpoied according to the fame divifions. The great I 4 ribs t3^ The Construction of Timber ribs which mark the feparate cones are objects indeed of wonder 5 thick, firm, green, and ftrait as lines drawn from the circumference by a geometrician ! It feems as if the effort of Nature in the conflru6lion and growth of this Tree had been placed here ; and that thefe ribs had out- grown the divifion of the feafon circles. Thofe o circles mark the ftops of growth between the Spring and Midfummer encreafe : it fhould ap- pear therefore that this Tree owned no diftindlion of thofe feafons ; but that it continued equally at all times growing on. 'Tis fingular in many things ; in nothing more than this. The Corona is fmall, but regular; and in the Pith are Veffels, ftufted, as the intima always are, with a concreted juice, like a hardened refin. ly. of the broad Seafoii Circles ia the Arbutus. The parts we wilh to note in Trees for their Angularity are beft fliewn by qppofition. In the Robinia Caragna the circles of the feafons fcarce exift : J'1.26 li O^JJ^J^ <:L4^^ G2^^ mf^%. d a :pi,'2 Arbjtttis V' V Explained by the Microscope. i;/ exifl : in the Arbutus, a Tree which few excerrd in delicacy, they are yet remarkably confpicuciK. A view of this is given in Plate XXVII. In the Rind, the Bark, and the Blea, a, h, c, nothing is particular ; but in the whole conftrudion of the Wood there is a delicacy which fancy fcarce can reach. There is much more : there is a difpofition of the Sap-Veffels ilrange and un- ufual i they are largeft toward the bafe of every circle, and become obliterated gradually to the verge. In the common courfe it is quite other- wife : but the line f, the mark of diftindion between the encreafe of a former and a latter feafon, is, in the Arbutus, thickened beyond what we fee in moft kinds : and even the exterior part of the firft circle from the Corona is thickened with it. The Corona, e, partakes of the delicacy of the whole flrudure of this beautiful fpecies -, and, tho' fmall and thin, and more than in moft other kinds tranfparent, affords a view of all its conftituent parts very perfedt, and very lovely. V. Of 13S The Construction of Timber V. Of the uneven Lines in the Wood of the Thuya Chinensis. Our attention was demandt^d, in a preceding^ inftance, by the perfed regularity in which the lines formed by the parietes and inner divifions of the Wood were drawn from the circum- ference to the center, even with a mathematical exaclnefs : we have here a proof how much Nature can deviate from what might feem her deftined rules ; yet without altering the con- ftruftion of thofe portions with the difpofition of whofe component parts fhe wantons. A fe(5lion of the Thuya Chinenfis, the China Arbor Vitae, is one of the moft delicate objecfls that can be placed before the eye : in this manner »tis reprefented at Plate XXVIII. The rays of lines which divide the Wood into innumerable fmaller cones are here thrown into an eafy wave, which, taking its rife from the inner line of the Blea, bends downward in the new circle, then riling in the fecond and third, takes again its nrfl: courfc in the inr.ermoft j and this with an Tin/Yi^ Cuij^jsi^szs ^1.26. w-" £ -d a Explained by the Microscope. 139 an eafy bend that is very pleafing. All the time the parts are as diflindt, and their quan- tities ^nd proportions are as regularly kept, and as well obferved, as if the lines had run with the mod perfed: ftraitnefs. For the reft, what is obrerv?.ble in this fine Tree, is, that the Pith is extremely fmall -, the Corona very delicate, but finely formed, and it runs into deeper angles than lis. ufually f;;en : the Sap-VelTels of the Wood are larged in the youngefl' parts of it ; and the Vafa propria exteriora are very dlAin^t, C II A P. 140 The Construction of Timber C H A P. V. Of Particularities in the Corona of T R E E s, I, Its Plainnefs in the C i s t u s Laurifolia. THERE can be no doubt but the con- flru6lion of this efTential part is perfedly the fame in all Trees : the flridtefl: obfervations, and the powers of the greateft glaffes, join to fliew this : but here, as in the Wood, and elfe- where, altho' the parts are invariably the fame, their difpofition differs wonderfully. In the Ciftus Laurifolia, Plate XXIX. the Corona is little more than a plain ring, a: in which, however, we fee eafily the fimple ilrudure of the C-ZSTus X^±u:eclfoxjo± ^ TL20 lli Explained by the Microscope. 141 the Bark ia the outer part, b^ unmixed with other' matter. In the portion next the Pith, that darker line it firft exhibits, r, fhews, when viawed with due advantage, the clufters, d, on which all future encreafe depends. For the reft, the coarfe form of the Blea, whofe outlines interfedling one another give cobweb-like ftars -, and forms of great variety and beauty. For the reft, the Annona is no trifling objed:.' Its Blea, ^, is greater in quantity and more dif- tindily formed than almoft in any other Tree. The Wood is regularly difpofed, and pierced by numerous Sap-Veffels, J^: and in the fub- ftance of the Blea, g, are Vafa intima, /6, greater than in many other kinds. II. Of the Pentangular Form of the Pith in the Almond. We need not always fearch the ftoves for Trees or Shrubs to afford delight in this exa- inination ; our gardens, nay in many inftances K 2 the 14B The Construction of Timber the hedges, afford them. If elegance of ftruc- ture alone were fought, and beauty were the obje(ft in purfuit, fcarce any kind affords it in a degree beyond the Almond. But befide this, it has alfo great Angularity -, and is in many parts moft worthy of obfervation. Plate XXXIII. In moil Trees the Pith, conforming it- felf to the other coats, takes the fame fhape with the outline of the Twig. 'Tis round we have feen in the Annona, and in the Olean- der 'tis elliptic, and angulated ; in each cafe, anfwering to the fliape of the Shoot : but tho' the Twig of an Almond Tree be round, the Pith is pentangular;/] This form is given it by the Corona ; which, tho' extremely narrow, yet preferves that fi)ape with the moil: trim exaCtnefs. The Pith anfwers in delicacy to the Corona ; and is tender, thin, tranfparent, and very prettily figured. But in the Almond there is more worth notice : the two Barks, a and /^, are thicker than is ufual ; and in the fubftance of the latter lie oval Vafa interiora, c, of great note. The Blea, j\^^ f . / Explained by the Microscope. 163 II. Their repeated Series in the Pis- ciDiA Carthagenensis. The finefl: view that it is poffible to obtain of the Vafa intima of Trees, is that of the Pifcidia Erythrina, given before ; where the Veflels were examined as to their ftrudure, in Plate XIII. but this other Pifcidia, tho' much inferior to that, is not without its lingularity or beauty. We have feen, in the HcHotrope, thefe VefTels lodged in their proper place, the Blea : Nature has there allotted to the Shrub a fin- gle line of them : here we have two, a b ; and the fecond is in a place altogether lingular, the Corona. The firft and more natural feries of thefe VelTels is ranged in the centre of the Blea: they are oval, large, and full of a juice, of a flrong green, utterly unlike and diftindl: from all the other contents of the Branch. The repeated feries occupies a confiderable fpace in the plain Corona of the Tree, where they have aifo loft their oval form. They are per- fedly cylindric, as is the moft natural fliape of L 2 thefe 164 The Construction of Timber thefe veflels ; and one would be led to doubt their nature, were it net afcertained by their contents; the fame very green hard juice filHng them. What is farther obfervable in this fpecies, is, the extreme number both of the Vafa exte- riora, d and of Sap-Veffels, J. There are feveral uneven ranges of the firft in the fub- ftance of the Bark ; and the latter occupy, with the fame irregularity, a very great part of the Wood : yet this Wood, e^ pierced as it is like a cullender, is not light, but very heavy. We fhould wonder at this, had not the familiar inftance of the Oak taught us, that the ftrength and weight of Timber is not afife(fted by thefe apertures. III. The central Difpofition of them in the Hemlock Spruce Fir. We have feen the Vafa exteriora enter the Pith, and flain it with their contents, in the Pinus Cembra : and howfoever it be out of the common c a d TL40 Explained by the Microscope. 165 common courfe to fee the Pith of Trees per- vaded by longitudinal VelTels, yet the Fir, known by the name of Hemlock Spruce, will ihew us that not the exteriora alone, but the intima, can find their way thither. A fecftion of this Tree is given, Plate XLI. The exte- rior range of thefe VeiTels is formed, juft where it {hould be ; in the Blea, a : they are fmall, but difiinguifhable enough to an accuftomed eye : they are perfedly round ; their coats have a remarkable thicknefs -, and they are fluffed full of a firm, red refin, not a little refembling what druggifts call dragon's blood. In the Pith we meet with Veffels, ^, round in their out- line, perfedly diflind in form from the cells of the Pith, and filled with this fame red refin. It is impoflible not to recognize the Vafa intima in thefe : they ftain the whole of the Pith, in cutting, with this juice : but the flight colour tiiat acquires by accident, is very eafily to be diftinguKhcd from the deep and coarfc contents of the Veficls themfelves. While this fedion is before us, it is impofiible hut we muft flop to admire the beautiful cor- flrudlion of the Wood, r, formed of lines drawA- L 3 with I 166 The Construction of Timber with a more than mechanical exadnefs, and enclofing Httle cones, d^ pierced with innu- merable Sap-VefTels, e. The Corona, f, pro- tuberates inward ; and, in a thin flice, is very diftind. CHAP. IV. Particularities of the Coronal Ve s s e ls : Their diftind Appearance in theSuMACH. IT has been fhewn that the Veflels of the Co- rona are^ot different from the feveral Veffels of the former kinds, only that they are here in a fmaller compafs, and of lefs fize. They need not be defcribed particularly after thofe j for greater and lefs is no diftindion in philofophy ; nor have thefe any other. Yet, as there is in Sumach an opportur«ity laid before the curious eye Km^^LL o CJBZ Stjittcse JFzh a //■>- "^/ TI.4./ ■tx^v Explained by the Microscope. 167 eye of being certified of this truth, it may be ufeful, as well as agreeable, to ilievv it. A fedtlon of this Tree is given, Plate XLII. where the firft fight will fhew how much it ap- proaches to the herbaceous tribes, in the glandu- lar conftrudtion of its Rind, and in its vaft Pith. Happily in this Tree the Corona makes a more diftin(ft circle, more defined in itfelf, and more feparate in its parts, than is to be Ceen elie- where. When we have followed the con- ftrudtion of this Shoot from without; and feen its brown and hairy Rind, a, lined by the dark green juicy Bark, l\ and within this the paler, yet green Blea, c, we diftinguifli very finely the cllipfes of Wood, {I; and within thefc the Corona. Its white circle, e, has let loofe, as it were, the cluilers, /'; and one of thefe^ feparated, waihed clean, and viewed by u greater power of glafi^es, appears as at Fig. 2. where the Rind and Bark, thrown to the ends» I. 2. fhev.' dots at 3. which are here the embryo Vafa exteriora ; and larger fpecks at 4. the interiora. At 5. in that which is to be the Elea, are dots, tho' fmall, yet particular ir. colour i and 'tis impoinble, both from that and L 4 from x68 The Construction of Timber from their place, to doubt their being Vafa intima in miniature : and in the central part, at 6. are Sap-VefTels, whofe openings, as is the cafe in moft other inftances, are fo big af almoft to look prepofterous. The Vafa exteriora, in the entire fedlion, can- not but be admired ; they are firm, full of a milky juice J and when the fedion, if of any thicknefs, has lain but a few minutes, they rife from its furface, being too folid to fhrink with the reft. In the Pith, at a fmall diftance, within the elufters of the Corona, g, are to be feen, very beautifully, purple VeiTels, ^, whofe form and ftrucfture fliews them Vafa intima. C H A P. Sv3i^cjr T/.42 §• ]i_ 7 '■".' ! .' i b a Explained by the Microscope, 169 CHAP. V. Of the Diflribution of the Sap-Vessels, particularly in the Oaks. TO form a proper judgment of thefc VelTels, too much mifunderftood by many, we can no where follow them better than in the Oak ; the firmeft, ftrongeft, heaviefl: of Trees ; yet pierced beyond all others by thefe tubes. They have been fhewn in their natural ftate in Plate III. in the common Englifh Oak : and that lize and diftribution of them, however ilrange it might fecm to an unaccuftomed eye, is not peculiar to the fingle fpecies. Nature is uniform in all her works ; and tho' there be few Trees, if indeed any, that have thefe openings fo large and numerous as the Scarlet andtheEngUfliOak,yet in all fpecies of 170 The Construction of Timber, &c. of that Tree they are very nearly alike. In the Scarlet Oak of America, fo pierced with them as to be unfit to contain, in vefTels made of it, any thing but dry goods ; they ftand much as in our Englifh kind, only not quite fo regularly. A view of this is given, Plate XLIII. There is a fort of triple rov/, a b c, formed of them in the Wood of each feafon, but not corre(5tly. TheSpanifliOak affords them in double rows. In the Ever-green Oak they have no circular direction, but run down obliquely crofs-wife. In the Chefnut Oak they are thrown into rays. And in the Red Oak, not the Scarlet, crols- v/ife. But in all thefe fpecies the proportion of aperture to folid is very nearly kept up, ex- cept in the Scarlet, where it is much greater than in any others. In the reft, where the VefTels are largeft, there are feweft of them ; and where fmaller, their number makes amends for their want of fize. INDEX. Sc^4JiL:aT OudJsi J^l-43 INDEX. A. Page CACIA 134 Alburnum ■ ■ 44. Almond ■ 148 Annona — ■ 146 Arbutus ■ ' ■ 136 Afli Maple — 106 B. Bark ■ • 41 Bark, its Ules — 38 Bark of Willow •— — — 116 Bark of Ozier — — 116 Bark, its Differences ■> • 116 Bark of the -Service Tree -~ 118 Blea INDEX. Page Blea » • 44 Blea, Its Particularities — . 121 Blea of the Liriodendron — 122 Blea of the Oleander • 124 Blea of the Nerium Zeylanicum — — 125 Blea of Willow 416 Blea of Ozier — — 417 Blea of the Ephedra 1 27 Branches " > ■ 97 C. Caragna ■ — 135 Circle of Propagation — • ^^ Circles in Arbutus 136 Circles in Thuya Chinenfis ■ 13B Ciflus Laurifolia 140 Clufters in Magnolia — 142 Cornus — ' 13^ Corona — — 5S — H^ Corona, Its Veflels 140 Corona, its Conftru6lion — — 58 Corona, its Parts — 5" Corona, its Veffels ' 58 Corona, its Particularities — 140 Corona of the Ciftus Laurifolia 140 Corona of Magnolia ' H' Corona I ]sr D E Corona of Staphylasa ■ Corona of Plucknetia Corona of the Oak — — Corona of the Bocconia — Cortex — Cortex, its Ufes X. CuprefTus Amer Cutting Engine Cyprefs D. Dog- Wood Dog-Rofe Engine Cutting Ephedra > — Growth ' — Hemlock Fir *^— "^"^ E. G. H. Page H3 144 59 60 38 153 4 153 130 112 , 127 - — r 97 » ' 164 Heliotropium INDEX. Page Heliotropium Arborefcens — - .■ 16 1 L. Larix — 154 Liber ■ — 41 Lignum — _— — ^i Liriodendron — - ■ — 122 M. Magnolia — _. 142 Medulla — ~— 65 Microfcope — n N. Nerlum Oleander . 124 Nerium Zeylanicum — 125 O. Oak, EngHQi — — 169 Oak, American -— — 170 Oak, Scarlet — — — 170 Oak, Red — — 170 Oak, SpaniHi — — - — 170 Oak, INDEX. Page Oak, Willow . . . - j^q Oak, Chefnut — -= 170 Oak, Evergreen * j^o Oleander — 124 Parts to obtain 26 Petraea — — — . ,. Pinus Cembra 149 158 Pifcidia Carthagenenfis ^ . , 163 Pith Pith, its Origin Pith, its Nature — — — 66 Pith, its Ufes — — - —.67 Pith of the Annona 146 Pith of the Almond 147 Pith of the Petra3a , 14^ Plucknetia — . — 144 Quercus Anglica Quercus Americana • Quercus Sempervirens — Quercus CalianeifoHa *— ^ 3 I N D E X. Page Quercus Salicifolla _ 170 Quercus Hifpanica ' 1 70 Quercus Rubra — — — - 170 R. Rind — 28 Rind, its Differences no Rind of Dog-Rofe — 112 Rind, its Ufes — — — 3 ^ Rind, its Conftrudion — 29 Robinia — — ^35 Rofa Canina — — —112 S. Sap-Veffels — — 88 Sap-Veflels, filling of them — 91 Sap-Veffels in Oaks 170 Seafons, Circles of 13^ Shoots — . — 105 Shoot, its Growth — 105 Staphylica — — — H3 Sumach — — ^^^ Tanacetum INDEX. T. Tanacetum Fruticans — 156 Thuya Chinenfis — ' 138 Timber, its Parts — 17 Trees, their VelTels 19 Trees, their Growth ■ 115 V. Vafa " ^ Vafa Propria Exteriora — — Vafa Propria Interiora — — Vafa Propria Intima -^— — 82 Vafa Succofa — — B8 Vafa Exteriora in Cyprefs •^- — — 153 Vafa Interiora in Larix — — 154 Vafa Interiora in Tanacetum Fruticans — 156 Vafa Interiora in Pinus Cembra 158 Vafa Intima — - 1 6 1 Vafa Intima in Heliotrope — — 161 Vafa Intima in Pifcidia Carthagenenfis — ■ 163 Vafa Intima in Hemlock Fir — — 164 Vafa Coronalia — — _ 94 Vafa Coronalia in Sumach — — 196 Veffels of Trees 15^ VeiTels Exterior — 72—152 VefTels Interior — ' 7^ — ^54 VefTels Innermofl — — 82 — i6r M VefTels N D Page VeiTelsSap — — — 88 W. Wood — — 51 — 130 Wood, its Conflrudlloii — 5 1 Wood, its Veffels 19 Wood of the Dog-Wood — — — 13Q Wood of the Acacia ■ — 134 Wood of the Robinia — 135 Wood of Pear-Tree . : 52 Wood of Bauhinia — ^ r 53 D I R E G- DIRECTIONS to the Binder. Plate Page I. to face -r ' 6 II. to face ■ 1 6 III. to face ' ^- 24 IV. to face -^— — 30 v. to face ' ■ 40 VI. to face — 42 VII. to face 46 VIII. to face — ' 54 IX. to face — ■ ■ 62 X. to face — yo XL to face — — ■ • 7^ XII. to face 80 XIII. and XIII. repeated, to face — 86—87 XIV. and XIV. -repeated, to face — 90 — 92 XV. to face 96 XVI. to face — — 102 XVII. to face 108 XVIII. to face • 114 XIX. to face — ^— 118 XX. to face 122 XXI. to face — — — 124 XXII. to face 126 M 2 Plate DIRECTIONS to the Binder. Plate ' Page XXIII. to face — — ■ 128 XXIV. to face 1 3 2 XXV. to face — — • 134 XXVI. to face • 136 XXVII. to face • — 137 XXVIII. to face - — ~ 138 XXIX. to face — 140 XXX. to face 142 XXXI. to face — — 143 XXXII. to face — 144 XXXIII. to face 146 XXXIV. to face XXXV. to face • 153 XXXVI. to faee 156 XXXVII. to face 156 XXXVIII. to face < 160 XXXIX. to face 162 XL. to face - — — 1 64 XLI. to face 166 XLII. to face — —- 168 XLIII. to face : 17Q %>L >4> ^1 jg^jMj m^-am^ f*l*Tt # ** vt *ij«i^'«'