=NOTE.=—The above multipliers are found as follows: Suppose _W_ to represent the weight of a body, _D_ its density, _V_ its volume, and _g_ the weight of the unit of mass, then _W_ = _DVg_. Now, if a cubic inch be taken as the unit of volume, then _g_ will be numerically 62.5 pounds. ———— 1728 62.5 Hence, _W_ = _DV_ ———— = 0.036201; 1728 π _DV_ = 0.03620 D —— _d_³ 6 (supposing _d_ to be the diameter, and the body to be spherical) 0.036201 × 0.5236_Dd_³ = 0.018955_Dd_³. If we now substitute for _D_ the specific gravity of cast-iron shot or shells = 7.000, we have, _W_ = 7 × 0.018955_d_³ = 0.134_d_³; and if for _D_ we substitute the specific gravity of lead, _W_ = 0.2142_d_³; and in case of powder, _W_ = 0.01744_d_³. _For diameters, weights and charges_, see Tables, pages 80-81. 35. When shot are heated to a white heat, what expansion takes place? ====================+=======+======+======+======+======+====== Calibre. | 8-in. | 42 | 32 | 24 | 18 | 12 --------------------+-------+------+------+------+------+------ Expansion, inches, | 0.149 | 0.11 | 0.10 | 0.08 | 0.06 | 0.04 --------------------+-------+------+------+------+------+------ 36. Do heated shot retain a permanent enlargement? Yes; in case of the 8-in. shot, for example, after the first cooling the enlargement is 0.054 in.; and, after the second, 0.099 in. 37. Are the igniting powers of a hot shot destroyed by ricochetting upon the water? No; a shot, properly heated, will ignite wood after having struck the water several times. [Sidenote: 97]] 38. What is the peculiarity of cartridges for hot shot? There are two cartridge bags, one being inserted, choke foremost in another of the next higher calibre, and the end of the latter folded under. 39. Explain the process of loading with hot shot. The piece should be sponged with great care, and the worm frequently passed into the bore. As a precaution, it is well to insert a wet sponge just before putting in the ball. The muzzle is sufficiently elevated to allow the ball to roll down the bore, the cartridge is inserted, the mouth of the outer bag foremost, the fold down, and carefully pushed home without breaking it; a dry hay-wad is placed upon it, and rammed once; then a clay or wet hay wad, and rammed twice; and finally, if firing at angles of depression, a wad of clay a half-calibre in length, or a wet hay-wad is put on the ball. 40. May the ball cool in the gun without igniting the charge? Yes, with proper precaution in loading. The piece, however, should be fired with as little delay as possible, as the vapor, which arises from the action of the hot ball on the water contained in the wad, diminishes the strength of the powder.