POPULAR SCIENCE MONTHLY. 



shop, where one pursuing special lines may make up his own in- 

 struments, construct his own machines, or devise models to be 

 used as patterns in the machine shop proper. The power for the 

 building is furnished by three dynamos and an engine located in 

 the basement. An air compressor and a vacuum pump form part 

 of the outfit. The laboratories are large, intended for several 

 students working together, or small, for individual workers. At 

 the present time, students are pursuing investigations upon the 

 mechanical equivalent of heat and the coefficient of viscosity of 

 a liquid. There are eight or ten of these individual laboratories 

 for single students, each supplied with all needed facilities. 

 Every laboratory room, large or small, is supplied with gas for 

 light and fuel, electricity for light and power, water, compressed 

 air, and vacuum pipes. In one of the two constant temperature 

 rooms is a highly interesting piece of apparatus conceived by 

 Prof. Michelson and perfected by Prof. Michelson and Prof. 

 Stratton. Its purpose is the direct production of standards of 

 length. The principle involved is the determination of the length 



of the metre in waves of light. 

 This determination was first 

 made by Prof. Michelson, whose 

 original investigation was pub- 

 lished by the Bureau Interna- 

 tionale des Poids et Mesures, 

 at Paris. The instrument pro- 

 duces light waves, from a given 

 substance, of known length, 

 and then mechanically lays off 

 standards of length, up to two 

 decimetres, in waves of light. 

 Another notably interesting 

 piece of apparatus constructed 

 by Prof. Michelson and Prof. 

 Stratton is a harmonic analy- 

 zer, which has cost two years of 

 work. A first pattern was quite 

 fully developed, only to be aban- 

 doned for the design shown in 

 the illustration on next page. 



The purpose of the apparatus is the analysis and synthesis of any 

 harmonic curve (Fourier's series), provided not more than eighty 

 elements enter into it. Every one knows the vast use made to-day 

 of traced curves in all branches of science. These curves are 

 frequently resultants and combinations of two or more simple 

 curves. It is a matter of difficulty to recognize and separate the 

 elements thus combined. The machine in question enables the 



FIG. 4. PROF. A. A. MICHELSON. 



