FIRED GUN-POWDER. Y/

shot acted on by the impelling power has pasted through incorresponding times. The second is to find by means ofthis movement of impulsion, the scale of retarded velocitiescorresponding spaces. To find the first scale, fire some'(Fig. 26.) rounds from the'point 8, in the direction Srwith equal charges, against a butt placed at the several dis-tances S a, S /, S m<, Sn. Now as two points on thesurface of this butt will be always known, viz. the pointwhere the line of direction S r falls, and that which the shotstrikes, the spaces 0 a, Ib, me, nd, pasted through by thegravitating principle, and the corresponding spaces so, s /,s m, s n pasted through in the same time by the movementof impulsion will be known, and the curve S abed describedby the projectile will be found. If the butt be placed atstteh a distance that the longest line nd of descent does notexceed 150 feet; the resistance of the air to the movementof gravitation will be inconsiderable, and the theorem

~ L

will serve to determine the time

t, that the (hot

is passing through the spaces oa, Ib, me, nd in its movementof gravity; and also through the spaces So, S /, Sat, S n inits movement of impulsion.

Fig. XXIV. Draw the directrix AE, making AB

— s/

32.18

oa, AC — \/

32.18

Ib, AD

= v^

32.18

me, A E = v —-— n d, and erect at the points B, C,32.18

D, E, the perpendiculars BH = So, CIt=S/, DK =S m, EL = S«; then a line passing through the pointsA, H, I, K, L, will be the scale of spaces pasted throughby the (hot in corresponding times, in its retarded move-ment of impulsion. From this deduce the scale of cor-responding velocities M N O P Q_, and that of the mo-mentaneous resistance of the air to the motion of the(hot; thus the retarding force of the air will be known,196. Jt has hitherto been supposed that the (hot is pro-jected in the direction of the axis, but this does not alwayshappen. To remedy this inconvenience; fire the gun witha charge that will produce a given initial velocity, place thebutt (Fig. 26.) at different distances 8 s, SI, 8^, S«,G taken