1904] 



On the Compressibility of Solids. 



309 



in the tube. It made three complete turns in Fig. 2. 



the length of an inch, and the undulatory form 

 was visible throughout one-half of the length of /""^ / 

 the wire. Instead of fixing new glass terminals, 

 I cut off the end of the copper wire, which 

 showed this curious seismic effect, and put 

 another wire in its place. An exactly similar 

 effect was produced on the magnesium wire, 

 when a glass terminal burst ; only the effect 

 was even more marked. The spiral produced in 

 the glass end was closer, and, indeed, the wire 

 had been shoved over itself and broken, for 

 magnesium wire is very brittle. The undula- 

 tions of greater amplitude extended through 

 the whole length of the wire, and there were 

 maxima at distances of about 35 cm. and 85 cm. 

 from the seat of the explosion. The bursting 

 pressure in this case was no more than 150 

 atmospheres, yet the effect produced was very 

 much greater than it was in the case of copper. 



The experiments with gold and aluminium 

 were carried out without the loss of a terminal. 



In the case of platinum, a terminal burst at 

 about 250 atmospheres, but it produced no 

 apparent seismic effect. On the last day of my 

 experiments I proposed to determine the com- 

 pressibility of a wire of mild steel, but, owing 

 to hurry in putting the apparatus together, it 

 was impossible to get any satisfactory observa- 

 tions, but one of the terminals burst, and at a 

 pressure over 250 atmospheres. Here again 

 there was no seismic effect. The platinum wire 

 had been thoroughly annealed before being 

 used, and the mild steel wire was as soft and 

 ductile as copper, yet, though copper showed 

 the seismic effect beautifully, it was imper- 

 ceptible in both platinum and steel. Before the 

 experiment with the steel, I supposed that the 

 high density of platinum caused the shock to be 

 opposed by more inertia than it could overcome, 

 but the density of steel is less than that of 

 copper, therefore its immunity to shock must 

 be due to something other than its density. 



The open ends of the glass terminals which are inside of the 

 tight collars are cut sharply off and the edges are not rounded 



VOL. LXXIII. Z 



water- 

 in the 



