This extract from Hutton enables us to divest the question of any technicalities, and puts it in so plain a garb that the simplest mind may comprehend it. Now, the great improvement of chemistry has been to extract from the nitre the gross material which is contained in the proportions—2-5ths impurities, and 2-5ths condensed air; thus, half the quantity being useless, the extraction of these alloys gives a greater quantity of condensed gases in the same quantity of matter; for if we take away 2-5ths of the proportions of useless matter, and supply its place with 2-5ths more condensed air, we thus get 4-5th explosive matter in the same bulk of material, and thus simply obtain an immense increase of power without an increase in bulk. We have here evidence of the progress that has been made in the science of explosive force.
Considering the difference between gunpowder in 1783 and gunpowder in 1858, I cannot say, with Hutton, that the force is doubled now to what it was when he wrote; but I believe that this would not be far from the truth; for it must be quite clear—if he is correct (which I believe he is) in saying the force of gunpowder consists in the quantity of explosive matter let loose and expanded by heat—that the greater the quantity of condensed matter we may have in any given weight, the greater the force, and the more rapid the explosion: purified saltpetre thus forming nearly pure gaseous matter; as the diamond is pure carbon. It seems singular, and is rather presumptuous to say, that Hutton was not much of a chemist; but had he been more so, he must have perceived that in the extraction of the foreign matter from the nitre, existed the means of obtaining an increased quantity of explosive power, and a proportionate increase of speed or velocity in that explosive material.
To ascertain the velocity best suited to all projectiles, constitutes the germ of the science; and that we are approaching a new era in even that more intimate portion of the science, is daily apparent. Science shows clearly that if a given force, a quantity to be correctly ascertained, can produce a certain result, the use of more is waste, and unworthy of the seeker after perfection; and thus we have to determine upon, or define, what is the degree or size of gun for certain effects: a mere calculation nearly allied to that portion of engineering which would define what power of engine would work a thousand cotton spindles, or raise a million gallons of water; and all this will eventually be done. Science requires that there should be no excess, no waste, no unnecessary recoil, and all that combined with the utmost range of projectile; this will have to be defined accurately before we can clearly or truly say we are masters of the science of gunpowder. True it is that the granulation of gunpowder gives a clear road to its attainment; but it will be a wearisome journey to reach the summit: yet it must and will be effected, and the nation that first attempts and carries out the attainment, will evince a real love for and mastery of science.
The following practical experiments illustrate the degree of velocity and the effects of projectiles so clearly, that they alone will convey some idea of the high velocity of the evolutions of the gases in gunpowder.
My experiments are, like Robins’, on a small scale; nor would I, like Hutton, try a brass gun of sixty calibres in length, carrying a one-pound ball; for one is strictly more limited than the other, and thus rendered the results laid down by him imperfect: for, as he says, “If you fill the tube with powder you get no greater velocity, as there is not a duration in the confinement to enable the powder to explode.” If he had assimilated the grain of his powder to the gun, he would have obtained a different result; and a knowledge of this fact, I apprehend, makes all the difference. The greatest velocity he obtained was with powder 11⁄2 times the weight of the ball in a gun of sixty calibres in length, and the velocity he then obtained was only 3,181 feet per second. The inferences that probably induced him to recommend others not to endeavour to obtain a greater velocity than 2,000 feet per second, were, like these experiments, drawn from imperfect data. With a ball of an ounce weight in a barrel of sixty calibres, and with 3-4ths the weight of ball in powder, or 12 drachms, a velocity can be given to the ball to equal it in force to 46,875 pounds. The velocity of this ball I leave to the calculations of the mathematical world. But, however, I will give the results of a round of experiments tried to ascertain this; and if the data laid down be correct, that the velocity of a ball must be multiplied by its weight to find the force, the result will be the establishment of a system of velocity never yet dreamt of. I cannot but imagine that there exists some error; though where it is I know not: every deduction I have drawn is consequent upon the results hereafter described.
“The power required to force a punch 0·50 inch diameter through an iron plate 0·08 inch thick is 6,025 pounds, through copper 3,938 pounds. A simple rule for determining the force required for punching may thus be deduced:—
“Taking one inch diameter and one inch in thickness as the units of calculation it is shown that 150,000 is the constant number for wrought-iron plates, and 96,000 for copper plates.
“Multiply the constant number by the given diameter in inches, the product is the pressure in pounds which will be required to punch a hole of a given diameter through a plate of a given thickness.”
Now an idea struck me, that this would form a very good test of the comparative force of gunpowder, and I consequently commenced an extensive round of experiments.