PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 411 



carded the terms and symbols of the higer sciences. I have endeavored to 

 explain the subject clearly and intelligibly without their aid, as I know- 

 that there is a large class of persons who will prefer to examine the result 

 of my labors in plain terms, not interspersed with algebraic signs. 



Guns mounted in turrets, in the ordinary manner, are liable to the seri- 

 ous objection that a part of the port is always open, and projectiles, or 

 parts of projectiles, may enter, especially if an enemy aim to project his 

 sliot against the protruding muzzles of the guns, in which case, from their 

 liability to bound and rebound in the limited space inside the turret, they 

 would be fearfully destructive. This error is corrected by the adaptation 

 of a spherical gun to a turret, hereinafter described. 



The proper ventilation of a turret is also an important consideration. 

 Sudden and complete changes of the whole atmosphere within a turret, 

 constructed in the ordinary manner, would be required to remove the gases 

 of powder that enter it from the vent of the guns, and the gases liable to 

 flow in through the open space about the guns in the ports. It would be 

 undesirable to draw these gases downward into the ship or fort; and to 

 eject them by a current from below, would involve the passage of impure 

 air to the men occupying the turret to work the guns. In the actual shock 

 of battle, the exercise of the men must be violent, as their number must 

 be limited and their duty severe; hence the importance of superior venti- 

 lation. I have succeeded in relieving the subject of all this class of diffi- 

 culties, by devices for keeping the port and vent closed, in the manner of 

 mounting the guns, and working them by steam or by hand, with the 

 workmen and gunners below, hereinafter described. 



I propose first to describe a spherical gun, and a turret to which it is 

 adapted. The gun is designed to possess extraordinary strength, by rea- 

 son of the great thickness and peculiar arrangement of the different 

 materials of which it is composed, a large proportion of which are of low 

 cost and easy preparation, and to provide, approximately, complete com- 

 pensation for the unequal expansion of the same by heat. 



When it was found necessary to correct errors in time-keeping machinery, 

 clocks, chronometers, etc., due to variations of temperature, compensating 

 devices were provided, designed to take advantage of the different degrees 

 of expansion for certain increments of heat, exhibited by difierent metals. 

 A gun can be made of such a combination of materials as will resist the 

 pressure or expansive force of the powder, while it provides compensation 

 for the communication of heat to the inner metal, as completely as the 

 pressure of the powder alone has been heretofore provided for. As here- 

 inbefore stated, these considerations not applying to small guns, I shall 

 describe the manner of constructing a very large rifled gun to project a 

 shot weighing one thousand pounds. The gun to be spherical in form, and 

 when completed to have a caliber of fourteen inches, and to weigh fifty- 

 one tons, or about one hundred times the weight of the powder and pro- 

 jectile. It is composed of three metals — Steel, Bronze and Lead. These 

 metals expand, with heat, in about the following proportions: 



Steel expands 11 



Bronze expands. 1^ 



Lead expands 28 



