210 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1936 



WEIGHT OR GUN 



The weight is made of cold rolled steel, 10 inches in diameter and 

 20 inches long. At its upper end is a 1-inch drop-forged eyebolt, 

 to which is spliced a steel cable (%-inch diameter) 4 feet long. A. 

 self-releasing hook may be placed here if it is desired to leave the 

 weight on the bottom. The other end of the cable is spliced to a 

 ring of drop-forged steel, about 3 inches in diameter. This ring 

 constitutes the upper end of the apparatus, and it is at this point that 

 the ship's sounding cable is attached. 



The lower end of the gun is tapered to within 1 inch of the muz- 

 zle, causing the gun to have a 1-inch-thick wall for that length. One 

 inch from the muzzle are four holes, drilled radially, through which 

 a one-eighth-inch brass shear-pin may slip easily. The bore of the gun 

 is the only part that must be made with precision. This must be 

 reamed straight and smooth and must furnish a snug sliding fit for 

 the cartridge and firing-pin housing. 



CARTRroGE 



The cartridges (pi. 2) are made of stainless steel and are ex- 

 actly 2 inches in diameter and about 4% inches long. They con- 

 sist of three parts — a midsection, which is the powder chamber, and 

 top and bottom sections. Both ends of the midsection have small 

 circular ridges, which cut into copper disks and assure a tight 

 seal. The walls of the powder chamber are one-quarter inch thick, 

 and its bottom contains a recess into which a rifle primer fits exactly. 

 Over this is placed a copper disk, against which the bottom section 

 screws tightly. In the center of this bottom section is a small hole, 

 opposite the primer, through which the point of the firing-pin may 

 strike the copper disk with sufficient force to distort it and thereby 

 set off the primer. This primer disk, however, is thick enough to 

 prevent distortion of the primer by the hydrostatic pressure of the 

 water. It is also made thick enough to have sufficient strength to 

 prevent the primer from being blown backward out of its seat at the 

 moment of firing. Furthermore, the thickness of this primer disk is 

 so adjusted, with respect to the shape of the firing-pin point and the 

 strength of the firing spring, that the point will distort it enough 

 to fire the primer but will not punch a hole through it. When func- 

 tioning satisfactorily the blunt-pointed firing-pin punches a dome- 

 shaped depression in the copper disk sufficiently deep to fire the 

 primer, and then this dome has enough strength to support the 

 primer in its position against the high pressure of the main 

 explosion. 



