It appears that the weight of gas generated is equal to three tenths of the weight of the powder which yielded it, and that its bulk when cold, and expanded to the rarity of Common air was 240 times that of the powder; the barometer standing at about 30 inches. From this Robins concluded that if the fluid occupied a space equal to the volume of the gunpowder, its elastic force, when cold, would be 240 times the pressure of the atmosphere, when the barometer stands as above. Mr. Robins also considered that the heat evolved was at least equal to that of red hot iron, and he found by experiments that air heated to this temperature had its elasticity quadrupled, and therefore, that the force of gas from powder is at least four times 240 = 960, or in round numbers 1,000 times as great as the elasticity of the air measured by its pressure on an equal extent of surface. From the height of the barometer it is known that the pressure of the atmosphere is about 14³⁄₄lbs. upon the square inch, so that the pressure of the elastic gas generated by the combustion of the gunpowder upon the same area would be 14.75 by 1,000 or 14,750lbs. at the moment of explosion. He found that the strength of Gunpowder was the same whatever might be the density of the atmosphere, but that the moisture of the air effected it considerably, in fact that the same quantity of powder which would give a bullet an initial velocity of 1,700 feet per second on a day when the atmosphere was comparatively dry, would upon a damp day give no more than 1,200 or 1,300 feet. ~Velocity of gas~ The velocity of the expansion of the gas is a most important point, upon which depends, chiefly, the peculiar value of the substance as a propelling agent. Many of the warlike machines of the Ancients produced a momentum far surpassing that of our heaviest cannon, but the great celerity given to the bodies projected from guns by gunpowder cannot be in the least approached by any other means than by the sudden production of an elastic gas. Mr. Robins found that the flame of gunpowder expanded itself when at the muzzle of the gun with a velocity of 7,000 feet per second. ~Dr. Hutton’s calculation as to:--_Volume, Temperature, Pressure_.~ ~Temperature~ ~Expansion.~ ~How to calculate expansion~ ~Absolute force of gunpowder cannot be determined.~