1842.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



291 



a form being adopted for it that can very seldom be introduced at all. 

 So far from being inconvenient, a semicircle, with the throne placed 

 on the chord or straight of the room, either between columns, or 

 within a tribune forming a smaller semicircle, would have been better 

 adapted to the particular purpose than any other shape. It would 

 then, too, have been manifest at once that the room was especially 

 intended to be and to remain what it actually was, and that it had been 

 planned expressly for the use to which it was applied, and for no other. 



V. Wolff's remarks on the Berlin Museum are one of the ablest and 

 most interesting pieces of architectural criticism I have met with for 

 some time— searching, and perhaps a trifle too hypercritical, but the 

 building itself is one that will bear a little more probing than usual. 

 As to probing, it is not every critic who can perform the operation 

 dexterously ; neither is it every architect who relishes the idea of its 

 being performed upon himself. Well, therefore, would it be, were 

 architects to anticipate critics, and thoroughly probe their own designs 

 in the first instance, with an unflinching hand ; at least, well consider 

 what objections are likely to be made by others, and whether they can 

 be at all parried. 



VI. There is a note to an article upon Greece in the last Xo. of the 

 Quarterly Review, which stimulates curiosity not a little ; for it men- 

 tions a "magnificent" work by Demidov on the Remains of Grecian 

 Architecture, but without specifying anything farther than that the 

 text is in Russian, unaccompanied by either a French or English 

 translation of it. Whether it is worth translating in itself, is more 

 than the writer in the Quarterly can tell, for he confesses his inability 

 to judge of more than the plates ; yet he might as well have mentioned 

 the date, and something that would have served as a clue to others, 

 in making inquiries relative to a work not likely to be met with by 

 mere accident. It does not follow that because the reviewer himself 

 could give no account of it, no one else can ; and at any rate he might 

 have extended his note, and said something of the engravings, since 

 it is to them, it may be presumed, that the work is mainly indebted 

 for its "magnificence." As it is now some time since the Quarterly 

 Review has favoured us with any architectural paper, it would do 

 well to found one upon M. Demidov's work ; for if there is anything 

 fresh in the plates, there is in all probability some original matter in 

 the text — perhaps some original remark also, and if so, it is quite as 

 deserving of being communicated to the readers of the Quarterly as 

 Fanny Burney's "small-beer chronicles" about herself and the "sweet 

 Queen." It is to be hoped that Queen Victoria has no such chroniclers 

 and diary-keepers about her person. The court newsman gives us 

 quite enough of "small-beer" doings at the palace. 



ON THE STRENGTH OF TRUSSED GIRDERS. 



(From the American Journal of the Franklin Institute.) 



Details of some Experiments upon the Comparative Strength of Trussed 

 and plain girders of rvood, made at the Phdadelphia Exchange, dur- 

 ing the construction of that budding in 1832. By John McClure 

 and Ellwood Morris, C.E. Reported by the latter. 



The experiments which have been made upon the relative strength 

 of girders, trussed and untrussed, are so few — that the following de- 

 tails may be found interesting to persons engaged in construction ; 

 particularly as the mode of trussing by suspension, therein tested, is 

 becoming more and more extensively used in this country, and is 

 really susceptible of being made very serviceable in many situations. 



These experiments were undertaken with the view of ascertaining 

 the proximate value of wrought iron suspension trusses for girders, 

 whicli were about that time brought forward conspicuously here, as a 

 new and useful improvement in carpentry ; though at least in one in- 

 stance they had been used many years before in this country; viz., by 

 Lewis Wernwag, the celebrated carpenter,* who applied suspension 



* Mr. Wernwag. a German by liirtli. iniroigraied here in 1788, anil is the 

 mechanic who designed ami consiruciel ihe famous timber bridge of 340 ft. 

 span, over the .Schuylkill nver at Pliiladeliiliii. (recently destroyed by fire,) 

 besides inany other wooden bri.-lges of magnitiale and importance, in various 

 parts of the United States. 



bars, one and quarter inches square, to stiffen the main longitudinal 

 floor beams of the bridge over the Neshaminy creek, in this state, 

 which was built by him in the year 1S08. (See the annexed sketch 

 which represents a side view of the suspension truss used in the 

 bridge referred to.) 



■■?aij 



We have taken the pains to ascertain from Mr. Wernwag himself 

 the date of the construction of the Neshaminy bridge, as it carries the 

 application of the suspension girder truss somewhat further back into 

 past time, than has heretofore been expected; though the writer has 

 lately been informed by a gentleman distinguished for his antiquarian 

 researches, that such trusses were in use upon the continent of Europe 

 even antecedent to that time. 



The now recorded history of the wrought iron suspension truss for 

 girders, as far as known to the writer, is as follows: — "In 1821, Mr. 

 R. Stevenson, of Edinburgh, designed a bridge for the river Almond, 

 in which the principle of supporting a roadway by iron bars passing 

 underneath, was first adopted."* In 1 822 the same principle was 

 recommended by Mr. H. Palmer, to be applied in carrying his rail- 

 way, of a single line, over streams or vallies.'i' In 1824 Mr. A. Aitiger 

 submitted a suspension trussed girder to the Society for the encou- 

 ragement of Arts; to which we shall presently more particularly refer, 

 and which was successively applied to practice. In 1828 girders 

 trussed by suspending rods were used with manifest advantage in 

 several buildings, by Mr. Joseph Conder, who claimed the merit of 

 their invention, as did also Mr. A. H. Renton, Civil Engineer.j AIL 

 these gentlemen, however, without their knowledge, had been antici- 

 pated in this matter by Wernwag, at the Neshaminy bridge, as before 

 mentioned. 



In addition to the above, the writer may state that in 1833 he ex- 

 amined a wrought iron suspet-sion truss, which had been applied some 

 years before, on a large scale, to uphold the central parts of Flat Rock 

 bridge, (of 198 feet span,) over the Schuylkill river; which bridge — 

 constructed with very slender curved ribs of three inch plank — had at 

 that time yielded considerably, and since has fallen down. In 1834 

 he measured a horse bridge (built by Wernwag) upon the Chesapeake 

 and Ohio Canal, near Harper's Ferry, of ■')2 feet span, which was 

 trussed like fig. 1, the horizontal bar being 2G inches clear of the un- 

 derside of the outer floor beams, which rested each upon two inverted 

 queen posts of iron, diagonally braced against lateral motion, and rising, 

 as it were, from the angular points 6 and c. This species of truss has, 

 since that time, been applied to strengthen the girders of a number of 

 bridges in the United States, to which it is unnecessary bow to refer.^ 



Returning from this digression, into the recent history of suspension 

 trussing; we will now repeat, that in the Franklin Journal for 1S32, the 

 description of a mode of trussing girders with wrought iron rods, act- 

 ing upon the suspension principle, was extracted from the "Trans- 

 actions of the Society for the encouragement of Arts," and accom- 

 panied by two wood engravings. 



The plan alluded to was devised by Mr. Alfred Ainger, and siib- 



• Civ. Eng. and Arch. Jour., for Oct., 1841. " Description of tlie Foot 

 Bridge over the river Whitadder, at Abbey St. Bathans. Berwickshire ; by 

 J. R. Wilsun." 



T Palmer's " Description of a railway on a new principle.'' London. 



I Reg. of Arts, 2nd series, vol. ii, London. 



^ In connection with this branch of the subject, we must not omit to add 

 tlie following, from the same paiier of Mr. J. R. Wilson, (Civ. Eng. a:i(i .irch. 

 Jour., Oct. 1811.) already quoted. 



•' In 1833 a bridge was erected on the tension bar principle over an arm of 

 the lake of Geneva. It has 13 openings, of 55 ft. span, and is 25 ft. broad. 

 The same plan has been adopted for two foot bridges of 138 and 81 ft. span 

 respectively, erected several years since over the nver Ness, near Inverness : 

 and also for a bridge over tlie river Whitadder, in Ber«ickshire, at Huttou 

 Mill, designed hy Mr.Jardine. of Edinburgh, which consists uf three openings 

 of 50 ft. span. Mr. Smith, of Deanston, has erected a foot bridge of this 

 kind, 103 ft. span, near Donne ; and has also applied tension rods very 

 successfully, for supporting the floors of Deanston cotton works, where they 

 have been in use for many years." 



