Common-sense, engineering skill, will demonstrate, that according to the weight of matter to be projected must be the nature of the expellant; _accumulative_--until it has overcome the inertia of that matter, _accelerative_--until it has communicated to it the highest state of velocity its power is capable of effecting. If, on the other hand, it is inferior to this, science has not extracted from it the full _horse-power_ it contains; and we are uselessly expending force and destroying our engines by undue pressure being exerted on one part, and inferior pressure on another; whilst by a proper distribution of that force, durability of the cannon is insured, and from twenty-five to thirty per cent. more work may be obtained from an equal quantity of powder, provided its granulation be judiciously selected according to the area of the gun. There is abundant proof that on this engineering question we have hitherto worked by the “rule of thumb;” prejudice having been a stumbling-block, which nothing but stern necessity will remove. The authorities have but just discovered this, although their attention was directed to it several years ago. In the year 1852, I produced before the Small Arms Committee, at Enfield, a portion of gunpowder suited to the expansive rifle; it was tried to a limited extent, and dismissed with the remark, “We don’t think there is much in it.” Experience, however, has demonstrated the truth of my observations, for, in all extreme range shooting with the expansive or “Greenerian”-principled rifles, not only is considerably greater _accuracy_ obtained with it, but an _increase_ of range equivalent to fifteen or twenty per cent. Another advantage of using gunpowder of a suitable granulation is the absence of sharp recoil; and thus greater accuracy of range is obtained--accuracy of range and steadiness of weapon being inseparable. Large-grain gunpowder is not only a more effectual expellant than the fine grain, but is much more safe to use, for by using it the risk of bursting the barrel is much lessened; as a very simple illustration will show. If we estimate the force generated by the usual charge of 2-1/2 drachms (I confine the question to the 14-bore gun, for uniformity) to be 5,000 lbs., whether the powder be fine or coarse grain, it follows that the fine powder, igniting so rapidly, will exert all its force on the breech end of the gun; whereas the coarse powder, igniting less rapidly, distributes this force over the whole length of the barrel: hence the greater risk of a gun bursting with fine powder than with coarse. If we suppose the fine powder to be entirely ignited when it reaches half way up the barrel, then the force of 5,000 lbs. is exerted on the lower half of the barrel; but if the coarser grain is not entirely ignited until it reaches the muzzle, then the force of 5,000 lbs. will be distributed over the whole length of the gun.