Velocity of Transmission of Disturbances through Sea-water, 499 



taken except by such military officers as are in a position to avoid the 



imposition of difficulties about the obtaining of explosives. 



The general course of conducting an experiment was as follows : — 

 The gauges were got out, adjusted to their maximum sensitiveness, 



and generally overhauled. 



The whole number of torpedoes for the day's work were charged 



and primed. 



The gauges were taken out in a dinghy, and adjusted to their 

 supports on the piles by one observer. The electrical circuits were 

 completed and tested, and the firing wires were run out off drums, 

 and the ends buoyed at about 30 yards outside each pile, and in the 

 direct line of the two piles. 



The temperature of the water was taken at the surface, and at a 

 depth of 6 feet. 



Meanwhile the other observer got the chronograph adjusted, noted 

 the temperature of the tuning-fork, assured himself of the perfection 

 of the electrical firing arrangements, and smoked the glass plates. 

 All being ready, one observer (J. F. A.) generally assisted by 

 Mr. Proctor, the torpedo storekeeper, shipped a torpedo, and pro- 

 ceeded to the firing point, and there connected it with the firing wire 

 in the usual manner. 



The other observer (R. T.) made the final arrangements in the 

 chronograph hut, and saw that all the precautions to prevent prema- 

 ture explosion were observed. On receiving a signal to the effect that 

 the torpedo was ready, he replied by a signal to drop the shot and 

 run away. The end of the firing cable, previously carefully insulated, 

 was then connected to a wire passing into the hut. The plates of the 

 bichromate firing battery were then lowered into the liquid, and a 

 safety-plug was placed in the firing position. At a signal from the 

 party in the boat, the pendulum was allowed to fall, firing the torpedo, 

 and carrying the recording plate against the scribers connected with 

 the recording apparatus and the scriber of the tuning fork. Imme- 

 diately after firing, the trigger was reset, the safety-plug placed in its 

 second position, the battery plates lifted out of the solution, and the 

 cable insulated. It will be seen that no less than four separate and 

 independent acts of precaution were thus performed after each shot. 

 We have had no accidents of the nature of premature explosions after 

 several hundred shots, though once in boring a dirty guncottQn disk 

 with a brass drill, a partial explosion, happily without doing any 

 damage, took place. 



After the firing of the shot the party in the boat proceeded to row 

 past the other pile, and there fastened the next shot to its appropriate 

 buoyed cable. Meanwhile the observer on shore took the smoked 

 plate out of the chronograph, wrote on it whatever data were neces- 

 sary, allowed the pendulum to swing back, readjusted the scribers 



