A. M. Mayer — Researches in Acoustics. 



87 



the rubber washers press against the ends of the bar. This 

 pressure is further increased by flat rings which surround the 

 holes in the washers and are pressed against these washers by 

 means of the springs, D, D'. By this arrangement the sur- 

 faces of the ends of the bars are exposed, while the contact of 

 the washers on the bars makes a water and steam tight joint. 



Thus the bar may be surrounded with ice, or, with steam, or, 

 with a current of water of different temperatures, and be 

 cooled or heated up to its terminal planes, while the holes in 

 the washers allow the micrometer screws, M, M', to be brought 

 in contact with the terminal planes of the bar. Two helical 

 springs are attached to the column, A. The other ends of 

 these springs are fastened to rods projecting from the tube, T. 

 Thus the same pressure of contact is always made between the 

 bar and the end of the micrometer screw, M. The tube, T, is 

 supported in Ys, Y, Y', and the greater part of the weight 

 of the tube is taken off the Ys by helical springs fastened to a 

 frame above the apparatus. The tension of these springs can 

 be so regulated that the tube rests on the Ys with the same 

 pressure when the tube has steam passing through it or when 

 it is filled with ice. The column, A, and the Ys, Y, Y', are 

 insulated from the base of the apparatus by thin plates of 

 ebonite, e. Between the binding screws, E and E', and con- 

 nected by wires, are the voltaic cell, F, the galvanometer, G, 



