214 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1936 



provides an undisturbed half for control or future reference; the 

 other is used for investigation. Furthermore, the undisturbed half 

 provides a depth scale, from the surface downward, which is of con- 

 siderable value. It has been found convenient to split the half to be 

 examined, either in half again or into quarters. This is done with 

 each fragment individually, using a thin-bladed hacksaw or its 

 equivalent. The fragments may always be returned to their proper 

 place in the brass trough. 



SOUNDING PROCEDURE 



The procedure on shipboard was to fasten securely to the deck, at 

 a convenient jDlace, a strong board. This was made straight and fiat 

 by suitable wedges, and to it were fastened prepared chocks to hold 

 the gun, and also several chocks to hold the bit. These are so made 

 that, when the assembled apparatus is laid in them, the bit and 

 cartridge are lined up with the center of the bore of the gun. If 

 such guides are not provided, the small clearance between the gun 

 barrel and the cartridge assembly makes it exceedingly difficult to 

 push the latter into the gun. 



The apparatus is assembled in the chocks, the firing mechanism 

 cocked, and the safety pin inserted. A cartridge is loaded in accord 

 with the anticipated need. If it is the first sounding in a new 

 locality, it is advisable to provide rather less than the anticipated 

 required energy. Subsequent loads may be increased as circum- 

 stances warrant. When all is ready, the cartridge is fastened in 

 place and the gun "loaded", by sliding the bit toward the gun, and 

 the shear pin is put in place. The apparatus is then hoisted over 

 the side. A man picks up the bit at the cutting edge, and, as soon 

 as the gun clears the rail, he drops his end over the side into the 

 water. The apparatus is immediately lowered until only the gun 

 is out of the water; this prevents swinging against the ship's side. 

 Finally, the safety pin is pulled out and the apparatus is lowered to 

 the bottom. With shallow soundings the explosion can be heard and 

 felt on the ship, and with deeper ones it can also be picked up by a 

 microphone or the ship's sonic sounder. "WTiere these failed to give 

 any indication, the cable was paid out until more than the antici- 

 pated depth was out, and then the apparatus was hauled to the sur- 

 face again. If it has fired, the gun and bit will be hanging sepa- 

 rately at the end of their respective cables, the bit supported in the 

 stirrup. If they are not so separated, and it is desired to bring the 

 apparatus aboard, the safety pin must be inserted at the earliest 

 possible moment while the apparatus is hanging clear of the ship. 

 Once this pin is in place the apparatus may be brought aboard with 

 safety. 



