L'Artizan . web de la poutre doit être faite assez forte towithstand. La souche qui peut être admis est de 4 tonnes par sectionalsquare". Si nous prenons le cas d'une poutre fixée à une extrémité et appuyée à l'autre, il n'y aura pas de déformation de cisaillement à un point - je d'o la jetée sur la poutre qui est prise en charge uniquement. Soit I  = 180 pieds, et10  = 2 à 5 tonnes ; ensuite, si x  = 13 pieds, la contrainte de cisaillement à ce point, whichwill être soit 54-5 m, ou 805 pieds de l'embarcadère qui prend en charge l'freeend de la poutre, va-t-il 13 x 2-5  = 32-5 tonnes ; par conséquent à ces pointsthe moins domaine de

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The Artizan . web of the girder should be made strong enough towithstand. The strain which may be safely allowed is 4 tons per sectionalsquare inch. If we take the case of a girder fixed at one end and supported at the other, there will be no shearing strain at a point distant - I from o the pier on which the girder is supported only. Let I = 180 feet, and10 = 2-5 tons; then if x = 13 feet, the shearing strain at that point, whichwill be either 54-5 feet, or 805 feet from the pier which supports the freeend of the girder, will he 13 x 2-5 = 32-5 tons; therefore at these pointsthe least area of the web should be 8-0625 square inches. This is of coursevery far below what would be necessary for the junction of the flanges. Before concluding the present paper we will make a few observationsupon the method, which we have adopted for the determination of the areaof the curve of moments of strain, from which arises a slight error, towhich we have already referred. Let a b c d in Fig. 2 represent the curv. i77ZM>. of moments, which is a parabola., b and c being the points of contraryflexure; then we have taken the area of the part b c g as being fff x 2 be This is perfectly correct. The area of the parts ahb, doi, we have takenas— = a h x h b — + d 1 x 7j-.a This is an approximation in most cases very near the truth, as the linesab, de are usually nearly straight. The correct expression for the area isevidently— _ 1 — -_. __ 1 _ ~ 3 ? fa • be - fg (hb + ic) +, g) • eg ad. li, and c i = v; If m = moment at centre of span, I =. span = a d, h bthen the area = . M I - (h + v) } - m (h + v)+ 1 . ^Jl.6 3 8 _ It will generally be found that the formula we have adopted is suffi-ciently correct, but we deemed it desirable to supply our readers with anaccurate account of our data, so that they may, ifthey choose, work outapproximations for themselves. All cur results have been compared withthose obtained by the process mentioned at the commencement of the paper,

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