436 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



of the ice had melted. He then applied heat to the top of a vessel similarly 

 arranged with copper top and clay sides, and filled with ice lumps and 

 water, and found that it melted very soon; all which he explained on the 

 principle that water is at its minimum density at 40° Fahrenheit, and that 

 when the ice touched the bottom of the vessel on the stove it became denser 

 and denser as it warmed towards 40°, and remained a non-conductor, the 

 ■ heaviest at the bottom. But when the heat was applied to the top of the 

 ice, then it melted into water, and as this water warmed towards 40° it 

 condensed and sank, carrying down heat to the ice below until it was all 

 melted and raised to about 60° of temperature. He concluded that water 

 conducted heat only by circulation, and not by transmission; hence, to melt 

 ice, apply the heat to the top or sides of a vessel. 



Field Artillery. 



Mr. Norman Wiard. — The United States field artillery carriage, of the 

 present day, of which more than twelve hundred have been ordered since 

 the rebellion commenced, is, in most essential particulars, the French 

 system of Gribeauval, of 1765. A slight improvement was adopted in 

 1827, viz., in making the trail single. 



The resistless force of public opinion caused some attention to be given 

 to rifled field guns at the beginning of the rebellion; but this was, how- 

 ever, mainly due to the attention given to the subject by that arch traitor, 

 Jefferson Davis, wdien in the cabinet of the United States, perhaps for the 

 purpose of entailing the expense of experiments on the government, in 

 order to use the knowledge so obtained, at a later time, to enable him to 

 subvert the very government affording him such facilities. But the new 

 principle was so imperfectly applied that rifled guns came very near being 

 discarded altogether. 



The chief errors in practice, however, resulted from retaining the old 

 standard carriages, designed for smooth bore guns; using projectiles of 

 double the weight for the same weight of gun, for the rifle guns; in 

 adopting calibers that were too large, and in using bronze, a material that has 

 been found, after careful experiment, not to possess the required endurance. 

 A six-pounder smooth bore gun was originally designed to deliver a 

 projectile of such a size as would allow a proper number to be carried in 

 one limber ammunition chest, and such shells burst into a suflScient number 

 of pieces to be very destructive within moderate ranges; but when rifled 

 guns came into service, the smallest projectile at first proposed was one 

 weighing fourteen pounds, for the James' caliber of 3.80. This caliber was 

 adopted, because U. S. six-pounder smooth bore damaged bronze guns 

 could be reamed out to that uniform size, and rifled. The weight of this 

 carriage and gun had been arranged for a projectile to weigh six pounds. 

 When the heavier projectiles came to be fired from them, the recoil was 

 found to be so great as not only to materially increase the labor of the 

 gunners, and affect the precision of aim, but it had the effect to destroy the 

 carriages. It was also found that the guns soon became enlarged in the 

 bore, which was accounted for by the increased strain upon them. It was, 

 however, chiefly due to the longer time the surface of the bore was exposed 

 to the heat of the powder. First, the heat expanded the inner metal, dis- 



