703 
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 UC-NRLF 
 
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George Davidson 
 
Paper Head for* the San Francisco Chapter, 
 AMERICAN INSTITUTE OF ARCHITECTS, 
 
1 (N ^ 
 
 THE IRON AGE. 
 
 Paper Read Before the San Francisco Chapter, 
 American Institute of Architects. 
 
 V. ERA OF MIND, OR AGE OF MAN 
 
 x f 
 
 BY G. H. SANDERS, F. A. 
 
 Gentlemen, Fellows and Associates of the San Francisco 
 Chapter of the A. I. A.: 
 
 Poom and Legend, Kable and Myth glow with the lustre of the 
 Golden Age, and every nation with a history, written or unwrit- 
 ten, has a background of romance which owes its brightness to 
 the same luminous source. 
 
 The writings of the poets and moralists of Greece and Rome, 
 through which the threads of authentic history have come down 
 to us, draw their inspiration from a far-away time, which, like 
 the lingering afterglow of a glorious summer's day, tells of an era 
 when the world was young, and mankind lived in simplicity and 
 innocence, and enjoyed a happy immunity from the incumbrances 
 and inconveniences of the, perhaps, overwrought civilization of 
 their and our day. 
 
 Both Hesiod and Ovid describe not only a golden, but a silver. 
 a bronze and an iron age, the former interposing the heroic age 
 between the bronze and the iron. The first four are also 
 mentioned as forming constituent parts of the great image of 
 Nebuchadnezzar's vision as recorded in Daniel one of the 
 Prophetical books of the Hebrew Scriptures. The mythology of 
 the ancients, as well as the clay records of Assyria, are replete 
 with allusions, more or less definite, to the same wondrous 
 epoch, as well as to the increasing degeneracy of the suc- 
 ceeding ages. 
 
 But authentic or fabulous as these may be, in the Genetic 
 record alone do we find a coherent, if only figurative, account 
 of a condition of things which could rationally afford an adequate 
 foundation for the all-pervading idea of the golden age. We 
 shall return to the subject in our concluding remarks, and will 
 for the present merely state that, of the four ages above recog- 
 nized, the last has been commonly conceded to be the peculiar 
 heritage of men of the present day. 
 
 THE AGE OF IRON. 
 
 But it is not the "Iron Age," of which we wish now to speak 
 so mush as the " Age of Fron," a much more definite and easily 
 apprehended, if less comprehensive idea, than that indicated by 
 the formsr term, which, indeed, may be taken to include the 
 whole range of the philosophy, sciences, arts and morals nay, 
 even the religion of the times, with all their respective concomi 
 tants and accessories which together make up the life of the man 
 of the nineteenth century. 
 
 But putting aside for the present the uncertain traditions, as 
 well as the myths and allegories of the days of old, the scientific 
 explorer of our times has collected, classified and arranged, in 
 orderly sequence, the evidences of at least three ages, neither 
 fabulous nor figurative, which have prevailed in former times. 
 These are known as the stone, the bronze, and our own iron age, 
 from the material which was most generally employed during the 
 respective periods in the ordinary implements of utility and 
 defense, all the stages of which may be practically existing 
 amongst various barbarous nations of our own day and generation. 
 
 This brings us face to face with our subject proper, and the 
 chief element of its title, viz.: Iron. 
 
 This is a substance of such world- wide utility that it is apt to 
 appear impossible to dispense with it. This, however, is disap- 
 proved by the history of past times as well as by the known con- 
 dition of many peoples and tribes of the present day, though their 
 position and status, indeed, may be said to be measured by the 
 degree of their knowledge and appreciation of this significant 
 material. 
 
 To fully comprehend the true position of iron in the scale of 
 life, we must glance at its position in the scale of creation. 
 Accepting as such the accompanying Geological section of the 
 shell or crust of the earth, we will ask your attention to a brief 
 examination of its component parts and the manner of their 
 formation the accompanying section (1) (from Geological Section 
 in Webster's Dictionary), which is generally taken to represent a 
 total thickness of about thirty miles, is just about the 330th 
 part of the diameter of the earth, or about the comparative 
 thickness of an ordinary egg shell. 
 
 The entire internal body of the earth has been supposed to be a 
 molten mass, and to properly understand this wo must begin at 
 the beginning, and the beginning, in this case, is 
 
 " NEBULJE." 
 
 In NTo. 2 we have a representation of the great nebula in Orion. 
 The latter is one of the most conspicuous constellations visible in 
 the southern heavens during the latter half of the year, and the 
 
 (No. I). 
 
 Post-tertiary, Pleistocene, or Quaternary. 
 
 Upper chalks, with flinta. 
 
 Lower chalk. 
 
 }( Portland stone and Purbeck. 
 Oolite \ Oxford group. 
 (Stonesfield elate. 
 
 ( Keuper. 
 
 / Trias. J Muschelkalk. 
 ( Bunter 
 
 Connecticut 
 
 Rivur sand- 
 
 stone, with 
 
 I foot-prints. 
 
 sandstein. 
 
 Pprmiaii ( Magnesian limestone, orzechstein. 
 ', "' "i Red sandstone and marls, or Roth- 
 ! liegende. 
 
 Coal measures. 
 
 Millstone grit 
 
 I Sub-carboniferous or 
 Mountain limestone. 
 
 *i 
 
 *> 
 
 3 -; 
 
 < = 
 r?. 
 
 < ^ 
 
 5 = 
 
 6. oaiakiil XvKvfKv/3 Catokill red sand- 
 Perio.l.v.WA-.VAvS stone. 
 
 4. Chemun7J p-hemung group. 
 
 Portage group. 
 Genesee slate. 
 Hamilton group. 
 
 Marcellus shale. 
 Upper Helderberg 
 limestone. 
 
 Schoharie grit 
 Cauda-galli grit 
 Oriskany sandstone. 
 Lower Helderberg 
 group. 
 
 I Saliferous beds. 
 Niagara group. 
 Clinton group. 
 
 Old red sandstone. 
 
 I Ludlow group. 
 
 / Aymestry limestone 
 
 L Ni M" ~i, >^%g? Medi " a sa " dst 
 
 "'''MS O rei( 
 
 Wenlock group 
 Upper Llandovery. 
 
 ) Upper Caradoc. 
 
 ida conglomerate. ) Lower Llandovery. 
 Hudson River group. 
 I'tica Shale. 
 
 [ Lower Caradoc. 
 
 Trenton. Black River \ 
 and Birdseye lime- ' Bala limestone 
 
 i>erio>1 - |jv : gi Po 
 
 stones. 
 Chazy limestone. 
 
 |i?^ Calciferous sandrock. 
 
 f Llandeilo flags. 
 
 'tsdam sandstone I 
 
 V Primordial zone. 
 
 I. AZOIC TIME OR AGE. 
 
 nebula is distinguishable by the naked eye, and constitutes the 
 sword-hilt of the figure. The nebula itself is one of the most ex- 
 traordinary objects to be seen in the heavens, and is, in fact, one 
 of the " show " objects of the astronomers. It is notable on ac- 
 count of its vast extent as compared with most of the other neb- 
 ulae, as well as its wonderful complexity and apparent confusion of 
 parts. It was one of the first objects examined by Lord Bosse in 
 his great six-foot reflector, and great was his joy and astonishment 
 to find the vast cloudy masses resolve themselves into myriads of 
 stars ! Some others of the nebulae are not as yet resolvable when 
 seen through the telescope. The spectroscope, however, is the 
 instrument especially relied on in investigations of this kind. 
 This curious instrument has the power of distinguishing the 
 chemical properties of substances by the light emitted by them 
 in an incandescent or highly-heated condition. In this way the 
 light of various mineral salts, gases and other terrestrial sub- 
 stances have been compared with the sun, the fixed stars, and 
 even the nebulcel Thus the " spectrum," as it is called, from 
 its shadowy character, becomes a sort of scale or gauge for the 
 qualitative analysis of all the rest of the universe; and it is every- 
 where found to be similar, if not altogether uniform, in properties. 
 
The spectrum is a luminous band 
 of prisrnatically-colored light. When 
 this is caused by a beam of sunlight, 
 the band or spectrum is seen to be 
 crossed by a multitude of bright, 
 colored and dark lines and bands. 
 When the light emitted by a va- 
 riety of metallic substances, gases, 
 etc., is examined, the lines they pro- 
 duce are found to agree with some 
 of those found in the spectrum of 
 the sun. The same is found when 
 the light of the fixed stars is ex- 
 amined, as well as the nebula;, and 
 terrestrial substances are found in 
 all of them! The nebula; are also 
 found to differ amon^ themselves, 
 just as the stars do, but in a differ- 
 ent way. Thus, some are found to 
 exhibit only the lines caused by the 
 two great gases, nitrogen and hy- 
 drogen ; and these have been hith- 
 erto found unresolvable into stars by 
 the telescope. Others show bands 
 only, and these are resolvable. < >th- 
 ers, again, show both bands and 
 lines, and therefore appear fo be of 
 a mixed or compound order, and in 
 which the original gaseous elements, 
 which appear to constitute the orig- 
 inal mass of all nebula, would seem 
 to be in process of conversion or 
 /(solution in the other cases com- 
 pleted or not yet commenced. 
 
 The latest accepted theory in re- 
 gard to these mysterious accumulations of serial substances 
 appears to be that, as these vast masses of "drift" are caught 
 here and there in the eddies arising from the inevitable friction 
 resulting from ethereal motion, aggregations of condensation 
 naturally oc':ur, and in the vast sweep of inconceivable ages, 
 under tlie influence of all-pervading Law, universes of har- 
 moniously balanced solar, planetary and lunar systems, with all 
 their necessary and appropriate accompaniments, come into 
 being. The diagonal of centrifugal and centripetal forces which 
 have arisen in the case of each initial eddy, establishes a center of 
 gravitational energy, which becomes in time a sun, and the sun, 
 in the progressive evolution of being, becomes in turn an earth, 
 and by successive condensations and depositions of the fiery 
 gases in the form of mo.'e and more solid materials, an orb, capa- 
 ble of receiving and sustaining life, slowly emerges from the 
 womb of creation, and a world of life is born. N The first rain- 
 drop which reaches the cooled surface of a new-born world 
 marks an epoch. The last that ever falls on the same earth 
 marks another. Between them lies the history of the life of that 
 world ! * 
 
 The condensation and deposition of material at first ethereal, 
 then gaseous, then aqueous, necessarily include phenomena 
 impossible to describe because incapable of being seen by any 
 other faculty than that of imagination. It can only be said that 
 what does occur must have taken place in the case of our earth 
 in the order here represented. (No. 1). 
 
 First : The igneous or primary rocks of the Azoic Age with 
 only the outer rim of which we can ever become acquainted ; 
 then depositions of material caused by erosion in the earliest 
 seas form vast strata which underlie all others and have solidified 
 
 GREAT NEBULA IN ORION. (No. 2.) 
 
 into the rocks of the second or Palezoic series, succeeded by the 
 Mesozoic and Cenozoic times or ages, and finally by the present 
 time or age, known as the age of mind, or of man. 
 
 The second or Palezoic series of times or ages are divided into 
 three great epochs, viz.: The Silurian age, or age of Mollusks; the 
 Devonian age, or age of fishes, and the carboniferous age, or 
 age of plants ; while the Mesozic corresponds to the single age 
 of reptiles, and the Cenozoic to the Mammalian age. All these 
 enormous periods are divided and subdivided again and again, so 
 that every strata has its place in the vast whole in such a way 
 as to be readily recognizable, if not by its intrinsic character- 
 istics, it may still be identified by those of its neighbors above 
 and below. But of the whole, it is with the upper third of the 
 second or Palezoic time, called the Carboniferous age, that we 
 have to do. The included strata are known as the coal measures, 
 and contains as well most of the workable beds of iron ore. 
 Associated with the coal measures also are vast strata of lime- 
 stones, including the sub-carboniferous or mountain limestones, 
 and superimposed beds of magnesian limestones the former 
 indispensable as fluxes, and the latter, recently found to be 
 equally valuable as a means of purifying the ore from the phos- 
 phorous and sulphur often contained in the coal used in the pro- 
 cess of converting the iron into steel. The iron ores, also, which 
 are principally worked, have themselves been largely the result 
 of plant growth, as by the process of absorption of metallic vapors 
 from the atmosphere by the vegetation, and the setting free of the 
 mineral thus held in combination by the decay of root fibres, etc , 
 the oxidized metal has been carried down and caught in the sub- 
 jacent sandstones and clay-stone rocks, and so has formed the 
 ferrugenous earths and beds known as Iron stone, Haemetite, etc. 
 We thus see in the very center of the scale, asso- 
 ;iated with tho great belt of the coal measures, 
 evidences of a time or age of extraordinary plant 
 growth and of conditions of solar, aqueous and 
 atmospherical phenomena unprecedented in the 
 life of our planet ; a time or age of light and heat 
 storage, and of strength and energy storage, and 
 of such other peculiar and suggestive combinations 
 as to justify to some extent the claims of these 
 same code measures as the real bona fide iron age 
 after all ; or at least it would appear that by the, 
 shall we not say, Providential provisions of the 
 law of natural selection, all the necessary elements 
 have been brought together for the development of 
 this present existing wonderful age or time, which 
 aH are ready to recognize as the ''Age of Iron." 
 
 The qualities of cast and wrought iron and 
 steel are so well known as scarcely to need men- 
 tion, except for the sake of reference hereafter. 
 
 TYPES OF STELLAR SPECERA. (No. 3). 
 
Fusibility, density and inflexibility in the case of cast 
 iron, and malleability, ductility and elasticity in the caso 
 of wrought iron or steel generally cover their respective 
 characteristics and constitute their valuable properties. Trans- 
 verse strength and resistance to crushing in the case of cast iron, 
 and of shearing in the case of wrought iron as well as the- still 
 more valuable capacity to resist tensile strains in the case of the 
 latter substance, are in every way enhanced in cast and wrought 
 steel, and still other valuable properties in wliat is known as 
 malleable cast iron. The Bessemer and other processes of con- 
 verting pig iron into steel, or, still better, directly from the ore, 
 bv forcing a blast of atmospheric air through the molten mass of 
 metal in a crucible, lias added so enormously to the availability 
 of steel as a lighter, stronger, and more reliable substitute for 
 ordinary iron, for almost all purposes for which the latter lias 
 hitherto been used, as almost to constitute as great a possible 
 development in manufactures and means of ulti mating great 
 enterprises, as the invention of the steam engine itself. 
 
 T1IK APPLICATION OF IRON. 
 
 But passing from this phase of the subject to the application 
 of iron in the arts of construction, we will note its progress as an 
 agent in the accomplishment of some of the great enterprises of 
 the century. 
 
 When James Watts was chicled by his parents for wasting his 
 time watching the action of steam on the tea kettle lid, they 
 little knew the tremendous revolution in the condition of the world 
 that the boy was destined to bring about neither more nor less 
 than the virtual inception of the age of iron, and thereby the 
 amelioration of the condition, and, shall we not say final civilization 
 of the habitable world, in a way unattainable by any other means. 
 The invention of the steam engine has led to the extension of 
 manufactures; the conquest of the ocean by the construction of 
 vessels of steel, rivalling in dimensions the famous Ark of old; the 
 extension of the land by the drainage of vast areas of bog, marsh, 
 fen. and lake; the cutting of canals, and the connection of oceans 
 by water-ways like great rivers; the covering of continents with 
 net works of steel rails; the prospective belting of the world by 
 i. leans of telegraphic cables; the conversion of our streets into 
 checkerboards of cable cars, our business houses into "cloud 
 capped towers" indestructable by fire: a-id the spanning of great 
 rivers and arms of the sea by enormous structures in the form of 
 bridges, before which the mightiest works of the ancients fade 
 into dolls' houses, and the very loftiest of which we have any 
 positive knowledge, are dwarfed into pigmies in the presence of 
 the Eiffel tower. 
 
 BRIIX ; Ks. 
 
 LONDON OLD BRIDGE. (No. 4.) 
 
 The first illustrations to which we will ask your attention are a 
 number of bridgt s. These useful structures have, in all ages, 
 taxed the ingenuity of engineers to construct, and may be said to 
 have bi-eii a mist important means of education, in enabling him 
 to surmount difficulties and achieve success in almost every direc- 
 tion in which his energies have been exerted. The first 
 structure we have here represented is Old London Bridge. 
 This is a striking example of the cumbrous obstructiveness 
 not unusual in the methods of the past. It was begun in 1 178, 
 
 by Peter of Cole Church, and was thirty-three years in building 
 Often covered with large and picturesque masses of wooden 
 buildings which were as often destroyed by" fire the main struc- 
 ture appears to have remained until the beginning of this century, 
 essentially as it was built. The next illustration, which is 
 New London Bridge, was designed by Mr. George Rennie, and 
 built by his brother, Sir John. This a beautiful structure; having 
 spans of 152 feet, and twenty-nine foot rise of arch, replaced 
 the old bridge which was removed to make way for it. 
 
 LONDON NEW BRIDGE. 
 
 (No. 5.) 
 
 Waterloo Bridge was erected in 1817, and is of a similar char- 
 acter to the preceding, being constructed of stone in many arches, 
 of less span, but in a wider part of the river. See next illustra- 
 tion. 
 
 But the next example is altogether different in material, if material used, as it is unnecessarily heavy and expensive, 
 not in form. Until recent years, stone, brick or timber was the 
 
 material almost always employed in the construction of bridges; 
 but late in the last century cast iron began to be employed, and 
 the specimen here shown Southwark Bridge over the Thames, 
 240 foot in span of arch, is not regarded as a success, in view of the 
 
 WATERLOO BRIIX 
 
 (No. 6.) 
 
 The next specimen here shown, the Menai Suspension 
 Bridge, (No. S.) indicates a great advance in the right direction. 
 The use of chains or links and wire cables on the suspension 
 principle began to be quite usual before this structure was com- 
 menced by Telford in 1819. It is 570 feet span, and has a versed 
 sine of forty-three feet for the curve of the Catenary. 
 
 This form of bridge, however, was not at this time found suit- 
 able for railways. The objection raised on account of vibra- 
 tion has been obviated by the principle introduced in the 
 next example, known as the Britannia Tubular Bridge, (No. 9) 
 designed and built by Robert Stephenson in 1845. It shows a 
 
 SOUTHWARK BRIDGE. (No. 7.) 
 
 complete revolution in the construction of bridges, which has 
 led to vast results. This bridge consists of two independent 
 wrought iron tubular beams 1511 feet long, each 15 feet wide 
 and 23 feet high at ends, and 30 feet in center. The central 
 pier is 230 feet high, and the two center spans are 460 feet each. 
 The land spans on each side are 230 feet each in length. The 
 top and bottom flanges of these immense girder tubes are cellular 
 
 in construction, and the floor and ceiling are strengthened by 
 keelsons and gi'ssets, and the side plates are strengthened by T irons 
 inside and out. See sec. (No. 1 1 ) This bridge, however, in this 
 peculiar form has only once been repeated in the Victoria Bridge 
 over the River St. Lawrence, in Canada which is 7,000 feet in 
 length, and whose spans are almost equal to those of the Britannia 
 Bridge. The mode of construction, the methods of floating the 
 
tubes into position and raising them into their places by hydraulic 
 pressure, and the final triumphant success of both these undertak- 
 ings, together with the interesting incidents and imminent risks 
 to which both were subject, owing to the dangerous condi- 
 
 tions attending their construction, has almost the interest cf 
 a romance, and IIRS raised both these enterprises, together with the 
 name of their designer, into a prominence which can never be 
 lost. Nevertheless, it is certain that they are never likely to be 
 
 MENAI SUSPENSION BRIDGE. (No. 8) 
 
 repeated, since more economical and advantageous 
 forms of construction have arisen from the principle 
 which they inaugurated, one type of which is the high 
 level bridge at Newcastle. (No. 12) This is a combi- 
 nation known as the bow string girder, an open tube 
 carried on a cast iron arch and wrought iron tie (see 
 plan and elevation) presenting an appearance of great 
 lightness and beauty both being more economical, and 
 avoiding the disadvantages of the close tunnel form 
 so objectionable in such long structures as the Bri- 
 tannia and Victoria Bridges, which shut out light and 
 air, and the fine scenery which'such situations usually 
 present; but even this form of the tubular bridge is 
 unnecessarily expensive, and the experiment is not 
 likely to be again made. It was simply a combina- 
 tion of the truss with the arch and tube, both of 
 which latter are wholly dispensed with in the next 
 
 IS 
 
 > 
 
 o * 
 
 6 a 
 
 s* 
 
 BRITANIA TUBULAR BRIDGE. (No. 9) 
 
 example, shown in elevation and section, which is the Newark 
 Dyke Bridge, Oubitt Engineer, erected in 1853. (No. 13) It is 
 the first, and a fine specimen of the Warren girder; and on account 
 
 of its economy of construction and freedom from any unnecessary 
 accessories, is a very frequent mode of truss construction, espec- 
 ially in America, in wood and iron, or both. 
 
 The next example is the Cruralin Viaduct, (No. 14) which shows 
 another fine truss on the same principle. It consists of 7 spans of 
 100 to 150 feet, and is carried on piers formed of hollow cast iron 
 columns, 12 inches in diameter, braced together in sections of 17 
 
 HIGH LEVEL BRIDGE AT NEWCASTLE, 
 feet 
 
 Top Plate represents the Elevation of one Span of Bowsting Arch of High Level Bridge 
 New Castle. Lower Plate is the plan of the same. (No. n) 
 
 (No. 12) 
 
 each in length. The trusses are of wrought iron, and 
 are 14 feet G inches in depth. The roadway is carried on the upper 
 string of this example, but placed on the lower string of 
 the Newark Dyke Bridge. The next example, (No. 15) is the 
 Saltash Bridge, which w^s erected by 
 Brunei!. It is known by the name of 
 "Fish" girder, on account of the construction 
 of the truss which is formed by reversed seg- 
 ments of circles of cast and wrought iron 
 plating connected by vertical and diagonal 
 bracing to which the roadway is suspended. 
 It is, however, less economical than the forms 
 of girders founded on the Warren type, and so 
 lias had no children. The next illustration 
 (No. 16) shows an example of a wrought iron 
 arch bridge over the Ehine at Coblentz. 
 But it is of no greater span, nor so econom- 
 ical in construction as many of the preceedino- 
 
 1 -J 11 8 
 
 rorms or bridges, and hence cannot compete 
 with then in universal adoption. The next ex- 
 ample (No. 17) shows the Fink type of truss. 
 In this girder each division comprises a 
 separate and distinct truss, all combined in 
 one by the boom or horizontal tie which 
 supports the roadway of the structure. It 
 is composed wholly of vertical cast iron struts, 
 inclined wrought iron braces, and one hori- 
 zontal tie. It is a worthy competitor of the 
 Warren girder as regards economy, but is less 
 pleasing in form. 
 
The Niagara Suspension Bridge, (No. 18) is the next example. 
 It crosses the Niagara River some distance below the falls at a 
 height of 245 feet above the water by a single span of 821 feet, 
 6 inches. The main structure is 
 a hollow rectangular box. The 
 steam cars traverse the upper 
 surface, while the carriages pass 
 through the tube. The walls 
 are formed of double vertical 
 
 ent versed sines has been criticised as a defect in the principle 
 of this bridge. 
 
 Tn this mode of construction the tube and the truss have 
 been combined with the suspension principle, as introduced 
 above, showing the progressive development of the idea of adap- 
 tation of means to ends, which is so marked a characteristic 
 of the present age, and the drawing attention to which is one of 
 the chief objects of this paper, especially in connection with the 
 
 l/V^fN/WWJVWWWV 
 
 timbers with wrought iron din.g- 
 
 o o 
 
 onal bars crossing between them. 
 
 The railway or upper floor is 
 
 carried by two wire cables, while 
 
 the carriage way or lower floor is 
 
 carried by two others, four in 
 
 all. The total sectioal area of 
 
 iron is 24 1 1 square inches. This NEWARK DYKK BRIDGE. 
 
 bridge was commenced in 1852. 8*0.13) 
 
 and open for traffic in 1855. It was designed and built by 
 
 Roobling, and cost .80,000. The use of the two cables of ditt'er- 
 
 NIAGARA SUSPENSION BRIDGE. (Xo. 18) 
 
 bolted together and braced laterally and connected by 
 wrought iron couplings, which were found better for 
 the purpose than steel. The tubular ribs are in sec- 
 tions 12 to 13 feet long, and from 1J to 2J inches 
 in thickness. It is designed to carry a double rail- 
 way below, and foot passengers above. 
 
 The next example (No. ?1) shows the great Garabit 
 Viaduct, lately erected by Mr. Eiffel. It is a combi- 
 nation of a wrought iron lattice arch carrying a lattice 
 trussed girder. It is of great height, 640 feet span, and 
 a very masterly work. It was built by means of sus- 
 pension cables, very much on the same principle, but by different 
 methods to that adopted in the Forth bridge shortly to be noticed, 
 viz., without scaffolding. 
 
 FINK TRUSS. (No. 17) 
 
 development of the same principle in architecture. The next 
 examples of Arch and Girder construction, the first in America, 
 and the other in France, show characteristic methods of spanning 
 great spaces by permanent structures on sound principles. 
 
 The St. Louis and Illinois Bridge, (No. 19) over the Mississippi, 
 is a fine example of metal arcli construction. It is in 
 three spans, the center 520 feet, side spans502 feet 
 wide respectively, and presents a novelty in bridge 
 building. The spans of the arches are among the w.dest 
 of the kind in the world. The rise of the center arch 
 is 47 1 feet. Captain Eads was the engineer, and he 
 must be credited with having designed and erected one 
 of the finest bridges of any age. Each span consists of 
 
 four double 
 
 inches diameter, 
 
 ARCH, BRIDGE AT COBLENTZ. (No. 16) 
 
 The Brooklyn Bridge, (No. 21 ) of which I here produce an illus- 
 tration, is the next great work to notice. It is 1,900 feet be- 
 tween supports, with piers 320 feet high, and is 250 feet above 
 
 CRUMUN VIADUCT. (No. 14) 
 
 the East River. It is a mighty structure, and a daring 
 and wonderful achievement. It also is a combination of 
 tubular truss to secure lateral stiffness, with suspension cables as 
 
 PART OF CRUMTJN VIADUCT. 
 
 est of the many magnificent undertakings brought *o a successful 
 accomplishment in recent years. 
 
 The Firth of Forth Cantilever Bridge (No.22 3) is another struct- 
 
 supporting agents. Cable cars, carriage roads and foot passen- ure of immense proportions, and of great complexity, being a com- 
 ger ways are provided, and the whole constitutes one of the great- bination of wrought iron arch-tubes, vertical and inclined tubular 
 
 
 
 "=2?A-<-2' 
 
 ST. LOUIS AND ILLINOIS BRIDGE. (No. 19) 
 
 columns or posts, pitching inwa-ds, double suspension bearings 
 latticed together, and gr^at latticed catenaries supporting a con- 
 tinuous box girder-tube which passes through the whole, carrying 
 the railway track. The span is 1,710 feet, besides the side ap- 
 proaches. It is constructed on the stab/eequlibrium principle, and 
 is wholly built of steel without scaffolding. It is without question 
 the most stupendous structure of the kind in the world, and will 
 
 scarcely be blown down like the Tay Bridge, in 1886. The 
 above structure is a combination of arch and catenary, with 
 the lattice principle. It is constructed by building out piece 
 by piece from each side of the central supporting piers. It in fact 
 provides its own scaffolding, and grows by gradual accretion of 
 balanced parts as a tree does, and on the same principle, thus 
 indicating a closer and closer return to nature by man as he 
 
2 
 
 assiduously studies her economic 
 processes. Nevertheless, the ap- 
 parent striking disporportion be- 
 tween means employed and ends 
 subserved is so manifest in this 
 structure as to suggest grave 
 doubts as to the soundness of 
 some of the principles of design 
 employed therein. 
 
 The next illustration here 
 shown (Nos. 23, 24, 25 and 26) 
 is the proposed great North 
 River Bridge at New York. 
 This enormous but beautiful 
 struct ire as it is designed, will be 
 fully twice as large as the great 
 Brooklyn Bridge. It is to be 
 2,820 feet span between sup- 
 ports. The towers will be of 
 stael, and 620 feet in height. 
 It will cost $40,000,000, whih 
 the cost of the former was only 
 15,000,000. 
 
 The bridge itself is formed of 
 latticed girders carried on lat- 
 ticed cables. The whole prom- 
 ises to be the grandest single 
 span structure that has yet been 
 conceived. 
 
 It will be seen that in each 
 of the above structures, while 
 
 the technical, the utilitarian, the objective qualifications have 
 in every case almost wholly governed the design, the result 
 has also partaken of the higher esthetic, ornamental and artis- 
 tic qualities in a remarkable degree. From the straight sim- 
 ple bar-like effect of the Britannia Bridge, imposing from its 
 magnitude and simplicity, to the great, sweeping curve of the 
 catenaries of the proposed North River bridge, each design 
 has presented features and combinations of features clearly ex- 
 pressed and resulting in a peculiar beauty which no mere 
 architectural accessory could in any way produce. Not one of 
 these designs depends for its effectiveness on any purely archi- 
 tectural detail as usually understood, but it is due entirely to the 
 proper distribution of parts in the most efficient way that could, 
 at the time, be reasoned out for the proper attainment of the ob- 
 ject in hand. This we have to insist on again and again. It 
 is the iron rule which can never be broken without departing from 
 true principle, and with unhappy results to the beauty of the 
 structure concerned, from the designing of the simplest moulding 
 to the construction of a cathedral, the erection of abridge, or 
 the building of a ship. It it the one paramount law in Art and 
 Science, as imperative in such an apparently variable and volatile 
 thing as a lady's bonnet, as in the construction of that useful, 
 beautiful and significant thing, the steam engine. 
 
 To evince the truth of this proposition we will present one 
 more well known, nay,thsperaps, in past times, somewhat hack- 
 neyed example, to close this series of illustrations of the very im- 
 perfect remarks to which you have so kindly and forebearingly 
 listened. I allude to the one great, significant, and really original 
 building of the century. The conception of no professional archi- 
 
 THR GREAT GARA BIT VIADUCT. (No. 
 
 tect, for no architect out of 245 who competed for it. prmrd 
 equal to the task. No builder; for none were found in the 
 length and breadth of England who could suggest such a struc- 
 ture; but of a mere gardener, a constructor of green houses. I 
 allude of course, to the Great Exhibition Building of 1S51. 
 Truly great it wns, and greatest, even, it will remain, until once 
 again the exigencies of the occasion shall override mere prece- 
 dent, and some future gardener shall produce as glorious a flower 
 from as small a seed, simply by yielding unquestioning obedience 
 to the needs of the occasion, unfettered by rule or any existing 
 order of things which could in any wav interfere with or en- 
 cumber pure utility. The design sprang into being, and the world 
 of that day was both astonished and delighted. It is said that 
 when all the designs for the Great Exhibition of '51 had been 
 received, classified and inspected, and the commissioners, rejecting 
 them all, had concocted one of their own, apparently as unsuit- 
 able for the purpose, as any one of them all, Joseph Paxton, 
 chief gardener to the Duke of Devonshire, sat down in 
 his office and in half an hour sketched out his design for 
 the proposed building on a sheet of foolscap. Sub- 
 mitting his idea to one of the Commissioners, he \vas en- 
 couraged to perfect it. The design was published and re 
 ceived the unanimous approval of the nation. The contractors, 
 Fox cfc Henderson, in one week prepared drawings and estimates, 
 and in four months from that date, 18 acres were covered with 
 glass and iron in a structure, the quiet be auty, majestic simplicity 
 and the unapproached convenience of wihch has been from that day 
 to this, absolutely unrivalled in buildings of the kind. Every 
 building of the sort since designed, has had a variety of accessor- 
 ies breaking up its mass by- 
 useless excrescences until the 
 fantastic structures have final- 
 ly lost every characteristic 
 which made tho original de- 
 sign great. The uccom pan- 
 ing views, show exterior and 
 interior views, and a few de- 
 tails. (Nos. 27, 2f , 29 and :!0) 
 The account of the design- 
 ing, and construction of this 
 building, reads like a fairy- 
 tale, in harmony with the 
 fairy like structure which was 
 the charming result. 
 
 Mr. Henderson, who made 
 every important drawining 
 with his own hand, working 
 18 hours a day for seven 
 
 TIRTH OF FORTH CANTILEVER BRIDGE. (No. 22) 
 
FIRTH OF FORTH CANTILEVER BRIDGE. (No. 23) 
 
 weeks, says in a speech made about that time, tiiat hundreds of 
 tons of glass were provided, of an unprecedented size; 
 thousands of columns, hundreds of girders 34 miles of 
 guttering pipes connecting the columns, which conveyed the 
 rain water to the ground, 205 miles of sash bars, and more 
 than 1, OQO,000 feet of flooring, were produced by the various 
 firms engaged in the work, in the short space of time which 
 was allowed to execute it. The setting out of the structure, 
 the placing of the base blocks on concrete filled into 
 holes dug in the ground, the raising of the columns, the 
 lifting of the girders and keying them into their proper places 
 in the structure, etc , proceeded with unexampled accuracy and 
 rapidity, and, the first of its kind, and unique in the history of 
 
 great expositions, the building was ready on the day when the 
 contract expired. This was clue to the entire simplicity and re- 
 duplication of every part of the structure, which again was due to 
 the harmony of scale, which in this structure, as in the Parthenon 
 and a few others, is perhaps after all, the most noticeable feature 
 in the building. 
 
 Contemplating the excellent qualities exhibited by this 
 great structure, which at the time of its erection, challenged 
 the admiration of men of taste and judgment throughout 
 the world, and in fact, elevated it to a level with the greatest 
 edifices ever conceived by man, it is evident that it in 
 no way differs in kind from any one of the great engineer- 
 ing works to which your attention has been directed above. 
 
 NORTH RIVER BRIDGE. (No. 34) 
 
 Adaptation of means to ends and that alone, in it, as in them, 
 constitutes and includes all of its qualifications, and in this as 
 in them, it is especially to be remarked that there is nothing 
 imitated. No attempt is made to transfer to one material the 
 appearance or proportions appropriate to another. On the con- 
 trary, each material is in its turn treated on its own merits, and 
 hence its value is thereby enhanced in proportion. It is just as 
 though the whole structure to its minutest part, was represented 
 by two sets of figures, indicating in the first place the intrinsic 
 value, in the other the value in application, and that both sets of 
 
 figures in every case, were identical. In how many structures 
 of the kind, erected before or since, can this be said to have been 
 attained. In other words that every material throughout the 
 structure should be so applied as to attain the greatest measure 
 of utility it is capable of, with the least expenditure of material 
 compatible with safety, and with the best artistic effect. Would 
 it be by adopting the forms and construction appropriate to some 
 other and very different materials? to make iron resemble stone 
 for instance, or wood iron or vice versa? It is evident that there 
 must be in such a case a great and useless waste of labor as 
 
well as material, in other words, that the intrinsic 
 and economical values would fail to agree. Note 
 the admirable way in which every part of the 
 above great building is adapted to every other 
 part! The way in which the columns rise from 
 ground to roof line, representing every one of the 
 direct lines of support throughout. The way in 
 which the connecting girders and filling in pieces 
 are keyed rather than bolted into their places, 
 and how directly and easily every part does its 
 duty, and how by the proportioning of material 
 to strength and position, such a degree of aerial 
 elegance is attained that it may, perhaps, best be 
 compared to the delicate twigs and branches of a 
 tree divested of its leaves, whose dainty pencil- 
 ings tax the skill of the artist fitly to represent. 
 When in the full glory of its utility, it overflowed 
 with a profusion of fabrics and materials, and 
 objects of beauty and use from every quarter of 
 the globe, it was like the same tree in full bloom, glowing with 
 verdure . with color and with fruit. 
 
 It seems at this point permissible to consider, as a compara- 
 tive test of the proper treatment of other materials, some of 
 the reeognized qualities and properties of Iron. Whether as 
 wrought or cast iron, or in the form of that now abundant material, 
 wrought and cast steel, innumerable tests and experiments have 
 settled to so large an extent the available qualities of all these 
 substances that there is no particular need of dilating upon 
 that subject further than may suffice to note some of the ways in 
 which they may be better used and less abused. In the first place 
 it must not be forgotten that all materials, without exception, are 
 subject to change, that no material, whatever its form or 
 qualities, is free from the liability to alter its shape; and 
 that therefore when a perfectly spherical cast iron ball rests 
 upon its side, it is no longer spherical, it is really oblate. 
 That a piece of cast iron ten inches square in section and a 
 standard foot in length, if placed resting on its extremities, ~ 
 is no longer a standard foot in length, and that when a 
 great weight is placed unsym metrically on any form of sup- 
 port, that support will be acted on unsymmetrically and will 
 change its form, and the arrangement of all its molecules 
 in the effort to adjust itself to the conditions thereby imposed 
 upon it, which in construction means a great deal, involving as it 
 does under given conditions the theory of re-crystallization, etc. 
 
 We are accustomed to suppose that our friends, the engineers, 
 are the men above all others who are used to taking account of 
 the minute changes in the form and direction of the substances 
 and forces with which they have to deal. 
 
 But architects are expected to abolish all such changes, 
 and to produce a structure of variable materials abso- 
 
 APPROACHES TO THE NORTH RIVER BRIDGE. (No. 25) 
 
 lutely fixed in form for ever; at least so one would suppose 
 from the "sort of criticism to which they are at times subjected. 
 But it is to be feared that they themselves are chiefly 
 responsible for the inappropriate use too often made 
 of materials, and the untoward results which frequently 
 occur. Uniformity of material means uniformity of action 
 in the changes which those materials inevitably undeigo 
 underthe influence of temperature and strain. Some of the \vnvs 
 in which iron should not be used, we beg now to note, 
 
 First: No great strain ought at any time to be thrown in nn 
 unsymmetrical manner on any unsymrnetrical section of cross iron. 
 This means an unequivocal condemnation of brarke/s. The extent 
 to which that mode of employing cast iron is used, is remarkable 
 
 CAST IRON BRIDGE AT CRAIGELLACHIE. 
 
 when the treacherous nature of the material so used is so well 
 known. 
 
 To founders and machinists who are well and practically ac- 
 quainted with the behavior of cast iron under strain and tem- 
 perature, there is nothing more objectionable than a large extent 
 of cross iron, as it is called. They refuse to trust to it under any 
 circumstances and yet we find in all the published examples an 
 almost unlimited use of this objectionable and dangerous feature., 
 Smooth, round columns of cast iron of small diameter,^ 
 are set upon end and a number of brackets are projected 
 from them at a sharp angle at cap and base plate, bearing 
 heavy loads of beams and arches and this for many stories in 
 height. Such an accident as occurred in the Owens Building, 
 at Chicago, or an unsuspected flaw in one of the brackets or any 
 other adequate reason, causing the snapping of one small section, 
 may possibly occasion in a moment the destruction of a large 
 building, hundreds of lives and much valuable property. Is this 
 either wise or necessary? Can bad construction ever be neces- 
 sary? Is it scientific? Isitartistic? That there are few authen- 
 
 TOP OP TOWER, NORTH RIVER BRIDGE. 
 (No. 26) 
 
 SPAN OF SALTASH BRIDGE. (No. 15) 
 
 tic cases of failure of this kind that can be referred to is no 
 argument in favor of the practice. Is it not something which 
 may occur under any sudden shock? The fall of compara- 
 tively few degrees of temperature, in view of the great inequality 
 between bracket and shaft, must cause unequal strains in both. 
 A settlement causing undue strain on any one part, or a local 
 rise of temperature, or some stress occasioned by any one 
 of a hundred different causes, may ultimate the con- 
 ditions which may bring about a failure such as I have 
 
BROOKLYN BRIDGE, NEW YORK. (No. 21) 
 
 indicated. Another wrong use of the material is indicated 
 in the ordinary form of cast iron girder in which the upper flange 
 is arched. This is an altogether mistaken idea, and an utterly 
 falUcious, improper, and unscientific use of material. In the gir- 
 der here shown (No. 31) the lower flange is straight; the shortest 
 distance between the two ends, in the upper flange, the ditance is 
 the greatest that can be found between the two ends. In cooling 
 flange (A) occupying greater length, shrinks more and flango 
 (l>) being shorter, shrinks less, in proportion; consequently there 
 is an internal strain set up between the top and bottom flanges 
 and brought to bear upon the web, which added to the weight 
 that the girder is supposed to bear, greatly lessens its effective 
 strength, if, (as in large girders of this form, is a frequent result,) it 
 does not occasion their destruction. This is one of the principal 
 reasons why such cast iron girders frequently snap, even befor^ be- 
 
 ing placed in the building. The ordinary form of the rolled girder, 
 indicates also the best general form for a cast iron girder under 
 ordinary circumstances. Parallel flanges, the upper one-half 
 the width and thickness of the lower, with square or in- 
 clined skewbacks at the end, indicate generally the best practical 
 form for cast iron girders of short span. (No. 32) 
 
 Tin; latticed girders used in the great exhibition building (No. 29) 
 were in every respect admirably adapted to the purpose for which 
 they wore intended; and either as stiffeners for the nave columns, 
 in which position, of course, they were much lighter, or as the 
 bearers of the gallery floors,they were found in every respect equal 
 to their work. 
 
 Before closing these perhaps too lengthy remarks, I will venture 
 to indicate a few ways in which it may lie found advantagfous 
 to use cast iron. Describe a circle in a square, ^No. 33) and lill 
 
 LONDON EXHIBITION BUILDING OF 1851. (No. 27) 
 
 in the angles of the square with other squares; apply the thick- 
 ness of one of the small squares round the circle internally, and 
 you have the section of a cast iron column of any diameter, and 
 any length within the prescribed limits of 30 diameters. In ele- 
 vation, place the flanges diagonally (as they are drawn) to the 
 length of the superimposed girders. Grow the flanges out bv 
 means of curves, into brackets of modraete projection and cast a 
 plate of equal thickness on top, andthe cap is formed. A greater 
 projection and a proportionately larger plate forms the base. If 
 supporting a great weight, as in the case of a basement column, 
 separate the base, and form circular flanges between the angle 
 ribs, on shaft and base sections, and bolt the two together. To 
 adjust wrought I beams to this form of columns continued two 
 or more stories in height; cut away the flanges of beams next the 
 columns on each side (using coupled beams) and fit the same to 
 flanges of columns, and bolt diaphram platos between the beams, 
 (which should always break joint) on each sideof column. In this 
 way a perfectly immovable system of columns and girders is formed, 
 symmetrical in bearing, and adjusted to the required conditions 
 throughout. The brackets are simply extensions of the ribs, 
 and there is 710 initial point of fracture, and the gird- 
 ers, on account of being firmly held at each end, will bear 
 double the weight of unfixed girders. If it is desired to fire- 
 proof these columns and girders, the shafts and brackets are 
 admirably adapted thereto. One other suggestion and I will con- 
 clude this section. The subject of Tempering is one which 
 does not seem to have attracted the attention of construc- 
 tionists to any large extent up to the present time. A 
 gentleman of my acquaintance in Ontario, Canada, some years 
 ago, patented a carriage spring of peculiar merit. Instead of be- 
 ing made in the usual way of several laminae of thin steel, secured 
 
 with rivets or loops, it was made solid, ogival in form, and tem- 
 pered in an oven. The reason why springs had never 
 been made solid before was because it was not easy to give 
 equal temper throughout the thick and thin parts. This was 
 secured by means of an oven of a peculiar kind. The ogival 
 form of the spring causes the bearing to be shortened with the 
 increase of load. Why is not this a principle which might be 
 taken advantage of in designing cast or wrought steel lattice 
 girders, (No. 34) and why should they not be tempered? The 
 tempering alone, the gentleman informed me, added 300 per cent, 
 to the strength of the springs. 
 
 The lately invented method of rendering iron unoxidizable, 
 known as the "Bower-Barf" process, by which a film of carbon- 
 ate of iron is formed on the surface of the metal, seems calculated 
 still further to increase the availability of iron as a building 
 material. 
 
 In conclusion, it is in order to revert briefly to the original 
 title of this paper, " The Iron Age." 
 
 While to speak in parables in the promulgation of truth and to 
 embody symbolism in the statement of principles has been, per- 
 haps, peculiarly characteristic of past times, and of people of a 
 genius different to ourselves, to clearly formulate the same princi- 
 ples, in logical terms and in unmistakable language, is believed 
 to be the special province of the philosophy of the present day. 
 And, while this may be conceded so far as it goes, it is also certain 
 that the wisdom of our own times still continues to be embodied 
 in, as that of other times must be interpreted by, modes of utter- 
 ance which condense into single expressions the ideas, sentiments 
 and general characteristics qualifying whole ages. Just such a 
 term is the one above mentioned, as expressing the peculiarities 
 of our own time or age. One, indeed, it is, in which the fallacies 
 
10 
 
 INTERIOR VIEW GREAT LONDON EXHIBITION BUILDING. (No. 28) 
 
 of the past are being tried in the furnace of modern scientific 
 research, and tiie pure metal of simple utility is being evolved 
 from the comparatively worthless philosophistical Haematite and 
 Iron Stone of former eras. And lo! everywhere and in every 
 sphere of human endeavor, order is emerging from confusion, and 
 progressive development takes the place of stagnation; and in 
 religion, politics, science and art, the symmetrical lines of the 
 Social Structure begin to appear and to assume an aspect in some 
 degree corresponding with the material improvements in so many 
 
 Diagonal Bracing used in 
 above building t(No .29) 
 
 directions visible round about us. In the pregnant words of the 
 Son of Amoz, luminous as they are with the true spirit of pro- 
 phetic utterance, " For Stones I will bring Iron '." But not only 
 must the useless representative of a false philosophy be ex- 
 changed for the rational science of an advanced civilization, but 
 the rotten symbol of a spurious morality must give place to a 
 more enduring substance in the Social Fabric of the day; for the 
 grand old prophet, with a rocket-like forecast of 3,000 years, 
 goes on to say, "For H'ood (I will bring) Brass !" But neither 
 iron nor brass nor the principles they represent will suffice the 
 great artificer who builds above the heavens! for the one will 
 rust and the other will tarnish, and the structures they build will 
 go to decay, containing as they do the elements of their own 
 destruction within themselves; for, though iron may be converted 
 from the coarsest "pig" to a substance lustrous as silver and 
 strong as adamant, it represents only a selfish rationalism at best; 
 
 DIAGRAMS SHOWING 31, V, 33 and 34. 
 
 
11 
 
 and, though brass may endure for a while and superficially burn 
 with a glory like gold, it exemplifies only the poisonous egoisms 
 of the age, and both ic and its antitype will blacken in time. It 
 is only another word for the conventional policy of the day. So 
 again the prophetic voice comes proclaiming across the centuries 
 in a still loftier strain: "For Iron I will bring Silver!'' Not 
 Rationalism and its fallacies, however scientific and intellectual, 
 nor mere morality with its sophistries, persuasive though they be, 
 can redeem the age or restore the lost lineaments of divine human- 
 ity to the race; but an enlightened spiritual philosophy, which is 
 also rational, must prevail, whereby the high principle which re- 
 gards the true well-being of mankind, in the broad sense of univer- 
 sal brotherhood, may be realized in the new social science 
 which must more and more mould the social organism of the 
 world. But not even silver alone,or the high principle it repsesents, 
 
 will suffice for the structure of the City of the Soul, for once again 
 the final promise comes as truly as of old, in divine prophetic utter- 
 ance.saying, "For Brass(I will bring) Gold." For the sympathies 
 and perceptions as well as the sensibilities and sentiments of 
 men must be aroused, and mediate good or the love of man, 
 represented by silver, must be vitalized tiy essential good or the 
 "love of God," represented by "Gold'' "like unto transparent glass." 
 And t/iese must be the substances out of which the mental, 
 moral, yea the spiritual 'habitations" of mankind must be con- 
 structed, ere the true Golden Age of perfected wisdom can come 
 again in place of tin- original Golden Age of untried innocence in 
 the prehistoric childhood of the race! Then, and then only can the 
 Spiritual Jerusalem be said to be indeed established among men, 
 in the good time coining, in the far offn'ons of futurity. 
 
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