a54 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[October, 



only been studied and cramped in the mechanical productions of the 

 school. My chief surprise is that he should for a moment doubt or 

 affect to doubt my sentiments on that head, when I have more than 

 once plainly stated — though perhaps in the very same terms I now use 

 — that I am not an admirer of any one style in particular, however ex- 

 cellent it may be, to the exclusion of all others. My architectural 

 creed is of a more liberal and comprehensive kind-, it is free from 

 those narrow sectarian prejudices that blind some to all beauty — all 

 merit that docs not come under the standaitl of their favourite style. 

 So very far am I from being one of those who can not only tolerate, but 

 admire even inferior productions, provided they do but belong — if 

 only nominally — to what they consider the only legitimate mode, that 

 as far as esthetic value is concerned, I hold the manner in which a 

 style is treated to be even of more importance than the question of style 

 itself. So long as the work itself manifests artistic spirit, feeling and 

 power, the particular language of the art, it happens to be composed 

 in, is comparatively of little or no moment, however important it may 

 be from other considerations attending any given case ; — so far at least 

 adopting Pope's doctrine that 



'■ M'hatc'cr is best administered is b"St." 

 By no means, was it my intention in what I first said to uphold the 

 Gothic in preference to all other styles, nor did I conceive that it 

 would be so construed by any one. And having thus cleared up S. L.'s 

 misconceptions— or at least his doubts, I may now leave him to call 

 Welby Pugin to account, as being a far greater offender — not only a 

 gtauiich advocate for Gothic, but so exceedingly intolerant withal, that 

 he would, were it in his power, exclude and uproot every thing else. 

 Yet, should he have read the Professor's " True Principles," S. L. will 

 probably not care to measure his strength with so redoubtable a cham- 

 pion. In case they should ever so encounter each other in argument, 

 they may probably be so well matched that each will make a convert, 

 —as such things have happened before now, and that S. L. will be 

 converted to Puginism, while Pugin goes over to " Paganism." 



Candidus. 



PROCSEDIIVGS OF SCIENTIFIC SOCIETIES. 



INSTITUTION OF CIVIL ENGINEERS. 



April G. — The President in the Chair. 



Experiments on ihe strength nf Iron Girders. By Thomas Cuhitt, Assoc. 

 Inst. C. E. 



This comnumication gives in a tabular form the results of experiments 

 upon upwards of 60 pairs of cast iron girders, varying in length between 

 7 ft. f> in. and 27 feet, with corresponding depths, and of all the forms usually 

 adopted for beams for buildings. They were proved in pairs by a hydraulic 

 press placed between them, the ends being retained by wrought iron ties. 

 The deflexion was noted at each increase of pressure, and in many instances 

 the beams were fractured. 



Sketches of the girders, and of the apparatus used for proving them, ac- 

 companied the paper ; from them five drawings have been made at the Insti- 

 tution to facilitate a reference to the information contained in the com- 

 munication. 



Description of an improved Level and Stand. By G. Townsend. 



This improvement lieing intended to procure a firmer basis and greater 

 fafility of adjustment than by the ordinary level, the autlior has adopted the 

 principle of the triangular plate, with three levelling screws, in the ordinary 

 instrument, with two pairs of screws, it has been found that the antagonist 

 screws, besides being apt to wear unequally, and to indent the lower plate, 

 are sometimes bent, and thus cause an unequal action upon the upper plate. 

 To. obviate these defects, the screws in the tripod level are made to work 

 into inverted cones, which are fixed in the three grooved arms of the stand 

 head ; the weight is more equally distributed, and the telescope more speedily 

 brought to a level. 



The telescope is fixed to the levelling plate by an upright limb, and to this 

 is added a small longitudinal cross level, as in C lavatt's instrument. In the 

 improved stand, each of the legs is attached to two arms of the lower tripod 

 plate, by which means a firmer basis is obtained. The usual locking plate, 

 to secure the levelhng screws, is also attached to this instrument, and kept 

 in place by a spring catch ; there is also a metal ring fixed on the upright 

 limb, above the arms, and which falls into three spring catches in the table 

 plate, by which any derangement from accidental violence, or in removal 

 from one station to another, is effectually prevented. 



A small circular spirit level is fixed in the stand in order to adjust it before 

 the instnuncnt he placed on it, by which means the labour of adjustment is 

 considerably abridged. 



April 20. — The President in the Chair. 



Experiments for determining the position of the Neutral Axia of rectangu- 



lar beams of Cast and Wrought Iron and Wood, and also for ascertaining the 

 relative amount of compression and extension at their upper and under sur- 

 faces, when snbjecteJ to transverse strain. By Joseph Colthurst. 



These experiments were undertaken in consequence of the difference of 

 opinion which has long existed respecting the position of the neutral axis of 

 extension and compression of iron and wood. 



first experiment. — Two series of experiments were made to determine 

 this point by cutting through the centre of each of a set of eight girders, 

 each ft. 6 in. long, 5 in. deep, and half inch thick, the first to the depth of 

 half an inch, the second to the depth of 1 inch, and so on, to the eighth 

 girder, in which only 1 inch of metal remained unsevered. The spaces cut 

 out were then filled with carefully fitted wrought iron keys, and the girders 

 were broken by the application of weights, in the expectation that these 

 weights would be some indication of the neutral point of each girder. The 

 results were, however, so irregidar, that no satisfactorj- deductions could be 

 drawn from them. 



Second experiment. — The next attempt was made in the manner suggested 

 by the late .Mr. Tredgold, by drawing two fine hues, 2} inches apart, on a 

 polished surface at right angles to a girder, in the middle of its length ; it 

 was then subjected to strain, and dimensions were sought to he taken to de- 

 termine where their divergence and convergence commenced, but the diffe- 

 rences were too small to be susceptible of accurate determination, otherwise 

 than by a fine micrometrical operation, which at the time the author had not 

 an opjrortunity of applying. The following plan was therefore adapted. 



Third experimejit. — In the side of a east-iron girder, ft. 6 in. long, 7 in. 

 deep, and 1 inch thick, a recess was planed at the centre, 3 in. wide by -| in. 

 deep. This was filed up ven,- true, and fourteen small bars of wrought iron, 

 with conical ends, were placed in it at regular distances of J an inch apart. 

 These bars were of such lengths as to hold sufficiently tight to carry their 

 own weight, and yet that the slightest touch should detach them. The 

 girder was then subjected to strain. The supports were 6 feet apart; 

 with a strain equal to 100 tt. the lower bar fell out ; as it was increased, they 

 continued to drop, and with 1500 Ih. all those below the centre had fallen. 

 The strain was then increased to 7000 lb., but no more bars fell. The centre 

 bar remained exactly as when put in ; all those above the centre became 

 firmly fixed, and were evidently under considerable compressive force. The 

 strain was then gradually taken off, and all the bars above the centre fell out, 

 their ends having become compressed by the sides of the recess pressing on 

 them ; they were of course too short when the girder resumed its former 

 condition, and the recess its previous width. These experiments were re- 

 peated several times, with pieces of fine wire and dry lance-wood charred at 

 the ends. 



The result in every case showed that the neutral axis of extension and 

 compression was certainly situated within -^ of an inch of the centre. 



Another experiment was still more decisive. A girder 9 ft. 6 in. long, 

 8 in. deep, 1 in. thick, was cast with two brackets or projections on the side, 

 each 9 in. on either side of the centre. A brass tube bar, with circular ends 

 and a sliding adjustment, wiis fixed between the brackets, which had been 

 filed true. Tlie clear bearing was 7 ft. 6 in. ; a strain of 50 tb. was sufficient 

 to cause this bar to drop out ; and with 250 lb. the whole effect of the pre- 

 vious experiment was produced. The tube, when placed loosely, 1 inch 

 above the centre, was held fast by a strain of 1000 lb. 



Wrought Iron. — Similar experiments were then made on wrought iron, 

 with precisely the same results, showing that the neutral axis, if not actually 

 situated at the centre, was nearly identical with it. 



Wood. — A similar series of ex))eriments, made upon wood beams, gave 

 exactly the same results as regarded the position of the neutral axis. 



From all the foregoing experiments, the author concludes that the neutral 

 axis of extension and compression in rectangiilar beams of cast and wrought 

 iron and wood, is situated at the centre of their depth, when those beamsare 

 subjected to transverse strains. 



Extension and compression. Cast Iron. — Experiments were also instituted 

 to ascertain the amount of extension and compression of cast and wrought 

 iron and wood. 



Upon a bar of cast iron, 3 inches square, and 9 feet long, two strips of 

 thin hoop iron were attached, the one on the upper, and the other on the 

 lower side, each strip being fastened to the bar at one end only, while the 

 other end was left free ; any change which occurred in the length of the 

 surface to which it was applied was clearly indicated. The differences were 

 recorded by very fine lines on a polished surface. The strips were 7 ft. C in. 

 long, and were bound to the whole length of the beam by bands of fine wire, 

 wound round and enclosing them at every 9 inches ; the beam was then sub- 

 jected to strain, and the following results were obtained : — 



6240 the beam broke ; good iron, showing a good clear fracture. 



It will be perceived, that until rather more than two-thirds of the breaking 



weight was put on, the amounts of extension and compression did not sen- 



