To determine the strength of powder in the easiest manner, is by comparing its effect with improved powder; as, for instance, by using a given weight of powder, as two ounces, and discharging a ball of a known weight, say 64 pounds, from an 8 inch mortar. The best cylinder powder generally gives about 180 feet range, and pit 180, with a ball and charge of the above weights; but the weakest powder, or powder that has been reduced, &c. only from 107 to 117 feet. The practice adopted in England, we are told, is, that the merchant powder, before it is received into the king's service, is tried against powder of the same kind made at the king's mills, and it is received if it gives a range of 1/20 less than the king's powder, with which it is compared. In this comparison, both sorts are tried on the same day, and at the same time, and under exactly the same circumstances. James (_Mil'y Dictionary_, p. 348) remarks, that the proof of powder as practised by the board of ordnance, besides that of comparing it by combustion on paper, is that 2 drachms, when put into the eprouvette, must raise a weight of 24 pounds to the height of 3-1/2 inches. According to Bottée and Riffault, before gunpowder is received into the arsenals of France, for service, it undergoes a variety of proofs; and the instructions for that purpose are contained under forty-two heads, embracing, at the same time, the specific duties of the officer employed for that service. The principal points, however, refer to a standard proof, made with the eprouvette, and differ, in no essential part, from the methods practised elsewhere. There is a uniformity in the French service, which cannot but be admired. In every thing which relates to the ordnance especially, even in the most minute details, the French, without doubt, exceed any other nation. Having examined the different kinds of proof, not only for gunpowder, but for cannon and small arms, as established by an act of parliament, it appears, that musket powder undergoes another description of proof. A charge of four drachms of fine grain or musket powder in a musket barrel, should perforate, with a steel ball, a certain number of half inch wet elm boards, placed 3/4 inch asunder, and the first 39 feet 10 inches from the barrel. The powder manufactured at the Royal Powder Mills generally passes through fifteen or sixteen, and restored powder, from nine to twelve. There are other contrivances made use of, such as _powder-triers_, acting by a spring, commonly sold at the shops, and others again that move a great weight, throwing it upwards, which is an imperfect kind of eprouvette. Dr. Hutton is of opinion, that the best eprouvette is a small cannon, the bore of which is about one inch in diameter, and which is to be charged with two ounces of powder, and with powder only; as a ball is not necessary; and the strength of the powder is accurately shown, by the _arc of the gun's recoil_.