8 
POPULAR SCIENCE REVIEW. 
simple function, of the velocity. The resistance of the air 
may he taken to vary as the sixth power of the velocity from 
950-1050 f. s., as the third power from 1070 to 1400 f. s., and 
as the second power for higher velocities. Under these cir- 
cumstances the cubic law, with a varying coefficient, has been 
adopted as the most convenient for calculation. 
That at 1,200 feet per second velocity this coefficient of 
resistance is the greatest for elongated projectiles, which rises 
in value rapidly at 1,000 f. s. to 1,100, and diminishes gradu- 
ally as the velocity is increased beyond 1,200. 
But for spherical shot the coefficient of resistance rises more 
gradually to its maximum at the same velocity of 1,200 f. s., 
and diminishes gradually for greater velocities. 
Dissected Table. 
Size and ■weight of 
shot 
Initial Velocity- 
Distance from gun 
Corresponding ve- 
locity at that 
distance 
Chilled Shot 
15-in. 
Eodman 
1501b. 
1001b. 
1 
681b 321b. 
181b. 121b. 
91b. 
61b. 
31b. 
2100 
2100 
2100 
2100 2100 
21002100 
210( 
2100 
2100 
8000 
7000 
6000 
5000 4000 
j 
3600 3100 
2700 
2300 
1900 
999 
910 
906 
898, 884 
857 854 
874 
884 
873 
Such a table as this for every hundred feet is of high value, 
being the first ever trustily obtain ed.* 
It is remarkable that no Artillery Manuals hitherto extant 
give any reliable information upon the decrease of velocity at 
different ranges. The old difficulty, the unknown irrepressible 
stumbling-block, the resistance of the air, vitiated every attempt 
at scientific conclusions. 
* Its great value may be at once seen from the solution of innumerable 
questions like the following : — 
A 6-pr. and a 32-pr. are both about to be fired with the same initial 
velocity of 2,100 f. s. : at what distance will the 32-pr. hit an object with 
the same velocity as the 6-pr. at 2,300 feet ? By the table we see 4,000 feet 
distance has a velocity for the 32-pr. 884 f. s., and for the 6-pr. at 2,300 
feet has a velocity of 884. 
Again, a 15-inch Hodman keeps up its velocity 7- at 8,000 feet equal to that 
of a 68-pr. at 4,100 feet, target distance. 
Tables have also been ascertained for finding the velocity generated by 
different charges, so that the following complicated question can now be 
solved : — 
A shot from a 9-inch gun (250 lbs.), fired at a target 200 yards' distance, is 
required to strike with the same velocity as it would strike at 1,000 yards, 
so as to compare perforating powers : what charges of powder must be used 
in each case P 
