374 



On the Compressibility of Solids 



With the assistance of Fig. I, its features, and the distri- 

 bution of its parts, will be apparent without any lengthy 

 description. It consists of three parts: the force pump on 

 the left, the receiver for the reception of piezometers or other 

 bodies on the right, and behind these, the block with tubes 

 projecting on either side to receive the rod or wire of the solid, 

 the compressibility of which is to be determined. Every part 

 of the instrument is made of steel. 



The characteristic and original part of the instrument is the 

 steel block with its tubular projections. After the experimental 



Fig. i. 



rod or wire has been introduced into the steel tube the glass 

 terminals are slipped over the extremities of the rod or wire, 

 and, passing through leather hydraulic collars, close the steel 

 tube. The terminals are then secured in position by open steel 

 caps screwed externally over each end of the steel tube. Each 

 of the glass terminals is commanded by a microscope with 

 micrometer eye-piece. 



In 1880, when the instrument was housed in a room with a 

 stone floor, these microscopes stood on three-legged stools, as 

 shown in the figure. As the room with the stone floor was no longer 

 available, I had to instal the instrument close to the windows of 

 the laboratory, which has a wooden floor, and fix metal brackets 

 in the wall to carry the microscopes. In both cases the micro- 



