130 
MINUTES OF PROCEEDINGS OF 
In figs. 4, 5, and 6, I have laid down, for the information of the 
Committee, the mean results of this practice, the observed trajectories 
being denoted by black, the computed by red, and for the sake of com¬ 
parison I have also shown, in blue lines, the departure of both curves 
from the parabolic. 
The annexed abstract will show how close is the agreement between 
the computed and observed ordinates in the curves delineated ; while a 
similar comparison for the majority of the curves observed, is made in 
the detailed report of the practice furnished herewith. 
Table XIII. 
Abstract of the Results of the Experiments made to ascertain the Angle 
of Projection and the Trajectories of the 1 2-pr. Armstrong Pro¬ 
jectiles when fired P. B., and at an apparent Elevation of 30'. 
Elevation 
given. 
Angle 
of 
Departure. 
Velocity 
at 
30 Yards. 
Initial 
Velocity. 
Ordinates at 
90 feet. 
150 feet. 
300 feet. 
Obs. 
Com. 
Obs. 
Com. 
Obs. 
Com. 
0 / 
o , // 
ft. per sec. 
ft. per sec. 
0 0 
0 25 44 
1188'1 
1197*5 
4*832 
4*832 
5-083 
5-097 
5*444 
5’459 
0 0 
0 25 55 
1170*7 
1179*8 
4-834 
4*832 
5-085 
5*118 
5*472 
5-443 
0 30 
0 48 35 
1179*6 
1188-9 
5-431 
5-441 
7-421 
7-44 
(continued) 
Ordinates at 
450 feet. 
600 feet. 
750 feet. 
900 feet. 
1,050 feet. 
1,200 feet. 
1,355 feet. 
Obs. 
Com. 
Obs. 
Com. 
Obs. 
Com. 
Obs. 
Com. 
Obs. 
Com. 
Obs. 
Com. 
Obs. 
Com. 
5-2 
5*255 
4-527 
4*483 
3-417 
3’133 
•869 
1-003 
- 
— 
— 
— 
_ 
_ 
5*202 
5-207 
4*425 
4-359 
2-75 
2-97 
- 
- 
- 
- 
- 
- 
— 
_ 
8-359 
8-329 
8*465 
8-414 
8-133 
8*025 
7*089 
7-056 
- 
5*428 
3*033 
0-45 
o-oi 
32. I may observe that the ordinates were first calculated upon the 
hypothesis that the resistance of the air was given by the equation 
f - ‘0003475 n K 2 v 2 — l 1 + ---1 
534‘3l 1 + 1426-4/ 
but it was found that the actual ordinates were more nearly represented 
by using the same constant (*0005213) as is used for smooth bored 
projectiles. 
The accordance of the ordinates calculated on this hypothesis are, 
on the whole, exceedingly close ; but it would be unwise to place too 
great dependence upon the results of experiments so partial, and carried 
on at such low angles. 
