54 



OBSERVATIONS AND RESULTS IN PHYSICAL OCEANOGRAPHY 



longest and most serious interruption was caused by the 

 failure of the oscillator on November 3, 1928. It was 

 not until Callao was reached that repairs to the oscilla- 

 tor could be made, since such repairs required dry- 

 docking. Consequently, no accurate soundings were 

 made between November 3, 1928 and February 6, 1929. 

 Beginning November 14, 1928 rough soundings were 

 made with an improvised shotgun. A steel breech just 

 long enough to hold a 16-gage shotgun shell was screwed 

 into one end of a length of brass pipe. The pipe acted as 

 a holder and also as a guide for a heavy steel firing pin 



which was dropped into the upper and open end of the 

 pipe, the shell end being held a foot or two below the 

 surface. The hydrophones were used to pick up the 

 echo and a stop wtach used to measure the elapsed time. 

 Soundings were taken in this manner twice a day. These 

 were only approximate because of the inaccuracy of the 

 stop-watch measurement and because of the uncertainty 

 of the velocity of a sound set up by an explosion. It was 

 a case of half a loaf being better than none, however, 

 and the device materially assisted in the routine occupa- 

 tion of oceanographic stations. 



