Some experiments have already been made in the laboratory on the flow of air, the results of which have been communicated by Professor Peabody to the American Society of Mechanical Engineers. It is now intended to continue the study of the flow of air and its use as a motive power in great detail, just as the flow of water is studied, and an air compressor of 100 horse-power, which will produce a pressure of twenty-five hundred pounds, is now being installed. [Illustration: THE 100,000 POUND BEAM MACHINE IN THE APPLIED MECHANICS LABORATORY.] The laboratory for testing the strength of materials was established in 1881 by Prof. G. Lanza, and has since been extensively developed under his direction, until it is now one of the most complete in the world. It is perhaps not too much to say that the experiments made in this laboratory have in some respects revolutionized the ideas of engineers. Previous to its establishment, the only tests of timber that had been made were upon small selected specimens one or two inches square and a few feet long. The results of these tests had been used for years by architects and engineers, and they were given in all the engineering handbooks. In the Institute laboratory there were conducted the first systematic and extended tests of beams of commercial size. The results soon showed that the strength of such timber was a great deal less than previous tests on small beams had indicated, and the practice of engineers and architects has since that time been completely modified through the results obtained in this and similar laboratories. In this way does the work of such a laboratory become of direct and lasting value to the arts. The central piece of apparatus of the Institute laboratory is the Emery machine, similar to the great machine at the Watertown arsenal, with a capacity of three hundred thousand pounds. But in addition to this machine there are a dozen or more other machines designed to test beams, columns, rope, wire and, in fact, materials of every kind and in every form. An interesting machine is that for testing shafts in torsion, and it is instructive to see it twist off with apparent ease a steel shaft three inches in diameter, twisting the fibers before they break till the rod resembles a barber’s pole. There are also beam-testing machines with capacities up to one hundred thousand pounds, in which not only beams but wooden trusses may be tested to the breaking point. Some of the apparatus is of great delicacy; for instance, one instrument will measure the twist of a steel shaft two and a half inches in diameter and six feet long so delicately that the effect of a twist given by one’s hand is distinctly visible; scientifically speaking, it will measure an angle of twist of two seconds. There is also a machine designed for testing stone arches, having a capacity of four hundred thousand pounds and suitable for an investigation of many questions concerning these uncertain structures;