216

THEORY AND PRACTICE

TRACT 37,

calibre, no less than between and of the powder escape*and is lost: and as the balls are often smaller than the regu-lated size, it frequently happens that half the powder is lostby unnecessary windage.

14. It appears too that the resisting force of wood, toballs fired into it, is not constant: and that the depths pene-trated by balls, with different velocities or charges, are nearlyas the logarithms of the charges, instead of being as thecharges themselves, or, which is the same thing, as the squareof the velocity.—Lastly, these and most other experiments,show, that balls arc greatly deflected from the direction inwhich they are projected: and that as much as 300 or 400yards in a range of a mile, or almost -jth of the range.

15. Proceed we now to state the deductions and applica-tions of the experiments made in the years 1787, 1788, 1789,1791. These experiments, we have seen, were chiefly in-stituted to obtain the effects of the air’s resistance to balls,in their rapid flight through it. To determine the resistanceto the very high velocities, were employed balls of threeseveral sizes, viz, of 2 inches, 2’78 inches, and 3'5i inchesin diameter. These were discharged with various degreesof velocity, from 300 feet to 2000 feet in a second of time ;and they were also made to strike the pendulum block atseveral different distances from the guns, in order to obtainthe quantity of velocity lost, in passing through those spacesof air; whence the degrees of resistance were obtained, ap-propriate to the different velocities. These series of resist-ances, for the three sizes of balls above-mentioned, havebeen obtained in a state remarkably regular, not only eachseries in itself, but also in comparison with each other; theterms in every one of them following a certain uniform law,in respect of the velocity, being indeed nearly as the 2^power of the velocity; and the terms of any one series also,as. compared with the corresponding terms of another, withthe' same velocity, these being in a constant proportion toone another, viz, as the surfaces of the balls moved nearly,pr as the squares of their diameters, with about ^ part more