RANGE (continued)

It was the opinion of engineers formerly, that by charging the pieces high, the ball was thrown to a greater distance. Hence the pieces were charged with two-thirds, or even the whole weight of the shot, in order to impel it with greater velocity; but it has been discovered since, that the half, or one third of the weight of the ball, is the fittest charge for the pieces.

If the whole quantity of powder, employed to charge the cannon, could take fire at the same instant, it is apparent that the velocity, communicated to the shot, would increase in proportion to the additional quantity of powder. But though the time of its inflammation is very short, it may yet be conceived as divided into many instants. In the first instant, the powder begins to dilate and impel the shot forward; and if it has force enough to expel it from the piece before the whole charge is inflamed, that part which is left to take fire afterwards will produce no effect at all on the shot. A charge of extraordinary force does not therefore accelerate the velocity of the bullet: and hence it follows that the piece ought to be charged with no more powder, than will take fire whilst the ball is passing through the chace of the cannon.

It may not be amiss to observe here, that the range of cannon is greater in the morning and at night, than at noon; and in cold, than in hot weather, The reason is, :that at these times the air being less heated, gives less way to the dilation of the powder, which being by this means confined, as it were, to a smaller sphere of action, must have a stronger effect in proportion (Belidor Bigot de Morogues).

"When the lengths of cannon are proportional to the heighth of the charge, the shot will be discharged with the same velocity, whatever the calibre may be; and since the ratios of the velocities of shots, issuing from pieces of different lengths, loaded with different charges of powder, will be of great use in the construction of cannon, we have collected them in the following table, where the numbers at the top express the length of the pieces by the diameter of their shots. That is, the first is 12 diameters; the second 15, and so on. The first perpendicular column expresses the charges, in respect to the weight of the shots: thus, ¼, ⅓, ⅓, ⅔, imply that the weight of the charge is ¼, ⅓, ⅓, ⅔ of the weight of the shot. The other numbers, in the same horizontal lines, express the distance in feet moved over by the velocities of the shot, uniformly continued in a second of time.

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