MECHANICS AND USEFUL AKTS. 67 



expected that very little water will be shipped as the piece is drawn 

 in. The gun being breech-loading, the water which enters the muz- 

 zle is easily disposed of, and it is claimed by Mr. Woodbury that it 

 can be fired again in the space of three to five minutes. In some 

 experiments made at East Boston, a twelve-pounder was fired under 

 water at a target made of spruce plank, crossed at right angles, and 

 heavily bolted and braced, and placed at a distance of ten or twelve 

 feet. The target was effectually penetrated. 



Doremus's Compressed Gunpowder. The following is an abstract 

 of the specification of the patent granted for this invention, which 

 has been adopted by the U. S. Government, and, after most careful 

 experimentation, also by the French (see Annual of Scientific Dis- 

 covery, 1862, p. 97) : 



The nature of the invention consists in taking granulated dry pow- 

 der, and placing a certain quantity to form a charge in a mould of a 

 cylindrical form, then submitting it to pressure under a piston, by 

 which pressure the dry powder becomes solid, and may be removed 

 from the mould and handled freely. Another part of the invention 

 consists in submitting two or more layers of powder in one cartridge 

 to different degrees of pressure, to produce what is called an " accel- 

 erating cartridge." The method of manufacturing these cartridges 

 is as follows : Moulds of the requisite size and fbrni are provided 

 with suitable movable pistons to fit into them. To make a cartridge 

 for a six-pounder gun, in which one and a quarter pounds of powder 

 constitutes a charge, this amount of granular dry powder is placed in 

 a cylindrical smooth brass mould, of such a diameter as coincides with 

 the bore of the gun, so that the cartridge will enter it. When the 

 powder is introduced a piston is placed upon it in the mould, and pres- 

 sure by a hydraulic or screw press is applied until the powder has 

 been condensed by a power equivalent to fifteen tons weight. The 

 piston is then taken out, and the compressed powder discharged, in 

 the form of a cylindrical cake, which may be handled without breaking. 

 In this form the granular condition of the powder is still maintained. 

 Other sizes of cartridges are formed in a similar manner. 



To make an accelerating cartridge, the method described is as fol- 

 lows for three degrees of combustibility : The powder is divided 

 into three portions : one of these is first placed in the mould and sub- 

 mitted to a pressure of twenty-five tons ; the second portion is then 

 poured in and subjected to a pressure of twenty tons, and finally to 

 the last portion there is applied a pressure of fifteen tons. The whole 

 of the powder placed in the mould and thus treated is now compacted 

 into one mass or cake, having three distinct strata of different degrees 

 of combustibility. That which has received the greatest amount of 

 pressure consumes less rapidly than the other portions. The rapidity 

 of ignition and burning of each is in proportion to the degree of 

 pressure to which it has been subjected. The requisite pressure for 

 such cartridges can only be ascertained by experiment. 



Powder in cartridges made in this manner by solidifying will resist 

 the action of moisture for a longer period than when in loose grains. 

 It will be also understood that these cartridges are cylindrical cakes 

 of powder, without paper or any other usual covering ; and as the 



