Testing to rupture actual bridge members is always a matter of great scientific interest, and while the record is quite extensive in eye bars, posts, or small parts, the great cost, time, and inconvenience of handling heavy girders has prevented experiment in that direction. In fact, the writer is unaware of any experiment upon compound riveted beams on a large scale, as actually used, until the experiment recorded below was made under his supervision. The beam was an exact duplicate of those in use on a bridge, about which more or less controversy had arisen as to their practical safety, and the test was made under, as near as possible, actual conditions of attachment and loading. The annexed drawing shows the form and proportion of the beam and connection with the posts, together with the position of the track stringers. The actual static loads to which the beam could be subjected by the heaviest engines in use on the road, with weight of floor, is 40,000 lb. at each stringer bearing, the strains computed therefrom being as follows: Flange strains at _m_, 3,800 lb. per square inch; at _a_, 5,700 lb. per square inch; at _b_, 6,400 lb. per square inch. Shear strains in web, between _a_ and _b_, 2,600 lb. per square inch. Shear strains in web, between _a_ and end, 8,000 lb. per square inch at least section, or where the web is 2 feet 4 inches deep, or 42 diameters between angle iron. [1] Abstract of a paper read before the American Society of Civil Engineers, November 16, 1887. [Illustration] [Illustration] _Rivets._--All rivets 7/8 inch diameter, or 15/26 inch when driven to fill holes; area of section, 0.6 square inch; bearing area, diameter × 3/8 plate = 0.35 square inch, and for 1/2 inch plate 0.47 square inch. Post attachment, considering all the twenty-six rivets doing duty, yields rivet strain as follows: In shear, single 5,000 lb. per square inch: and bearing area--1/2 inch plate--6,600 lb. per square inch.