river side, and in the city warehouses. It often happened that the pressure in the power mains was not sufficient for pressing purposes.

The apparatus known as an intensifier was then used, by which any pressure required could be obtained. Hydraulic power was also used at Westminster Chambers, and elsewhere, for the purpose of pumping water from the chalk for domestic use. The pump was set going in the evening and continued working till the tanks were full, or until it was stopped in the morning. For work of this kind, done exclusively at night, a discount was allowed from the usual rates. Mr. Greathead's injector hydrant, made at the Elswick works, had been in use to a limited extent in London in connection with the power mains.

A small jet of high pressure water, injected into a larger jet from the water works mains, intensified the pressure of the latter in the delivery hose, and also increased the quantity. By this means a jet of great power could be obtained at the top of the highest building without the intervention of fire engines. This apparatus enabled the hydraulic power supply to act as a continuous fire engine wherever the mains were laid, and was capable of rendering the greatest assistance

in the extinction of fire; but there was an apathy on the subject of its use difficult to understand. In Hull the corporation had put down a number of these hydrants in High Street, where the hydraulic power mains were laid, and they had been used with great success at a fire in that street. The number of machines under contract to be supplied with power was sufficient, with a suitable reserve, to absorb the full capacity of the station at Falcon Wharf, and another station of about equal capacity was now in course of erection at Millbank Street, Westminster. The works had been carried out jointly by the author and Mr. Corbet Woodall, M. Inst. C. E.; Mr. G. Cochrane had been resident engineer and superintendent. The pumping engines, accumulators, valves, etc., and a considerable portion of the consumers' machinery, had been constructed at the Hydraulic Engineering Works, Chester. Sir James Allport, Assoc. Inst. C. E., who was the first to adopt hydraulic power for railway work, had been associated with the enterprise from the commencement of its operations in 1882. His wide influence and extended experience had greatly assisted the commercial development of the undertaking.

TEST OF A WROUGHT IRON DOUBLE TRACK FLOOR BEAM.[1]

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.

Larger.

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.

Connection of ³⁄₈ Web to Flange Angles.—Taking the forty rivets between ends of girder and second stringer, the horizontal strain difference is 162,000 lb., the rivets being strained 3,400 lb. per square inch double shear, and 11,600 lb. per square inch bearing area. Taking distance from ends to first stringer, the horizontal strain difference is 105,000 lb., yielding on twenty rivets 4,200 lb. per square inch double shear, and 15,000 lb. per square inch bearing area. Taking a short distance of 2 feet from ends, the horizontal strain is 70,000 lb. on ten rivets, giving 5,800 lb. per square inch double shear, and 20,000 lb. per square inch bearing area. In these girders the weakness feared was in the end flange riveting and shear in end web, and caused the test recorded below. The test was recently made at the works of the Keystone Bridge Company, by means of hydraulic power applied at stringer points. Convenience made it necessary to make the test with the beam blocked up horizontal on the ground, so that the weight of the beam is necessarily neglected. The beam was connected with a pair of posts, precisely as in the actual structure, between which an additional girder was framed as a reaction base for the rams. The annexed diagram shows the general arrangements. The hydraulic power was derived from the testing machine plant of the Keystone establishment, and the deflections measured from a fine wire parallel to the lower flange, and about 3 inches therefrom. The diameter of the ram was 10 inches; area 78.54 inches. The record was as follows: