HITTING THE MAEK, ETC. 
9 
When the celebrated gun of Sir William Armstrong, F.R.S., 
was first tested, the range was found to greatly exceed what it 
ought to have been by theory. Grunnery was all at sea for 
high velocities. The first elements, obtainable only by experi- 
ments at successive points of the path of one and the same ball 
were really unknown. 
It is stated in these Reports (page 20) : — 
“ Round 68, with 5-inch rifled bronze gun, permanently injured 
the gun.” . . . “Nothing wrong was noticed before the eighty- 
fourth round. The resistance of the air was found to be three 
times its proper amount.” This diagnosed unsteadiness. The 
shot was tilting itself in its flight, creating greater resistance. 
Again they say : “ When we came to experiment with the new 
5-inch M.L. gun, converted from a breech-loader, we found the 
resistance of the air for shot fired from this gun less in propor- 
tion than for any other calibre. We could only ascribe this 
reduced resistance to superior steadiness of the shot. The gun, 
when tried on long ranges, made remarkable good practice. 
Hence it is manifest that any chronograph which is capable of 
recording, in a satisfactory manner, the time at which the shot 
passes a succession of equidistant screens, affords a ready means 
of testing the degree of steadiness imparted to the shot by any 
new gun or new system of rifling.” 
The enormous labour of comparing each velocity at each of 
the screens for a considerable number of rounds may be easily 
imagined.* 
The results of these beautiful experiments and researches are 
of the utmost importance — 
(1.) In the technical education of artillery officers. 
(2.) In the assistance they give to the practical artillerist. 
The ascertained laws of flight will now present artillerists 
with a true guide for the performance of their arduous duties. 
The result of 18 rounds of shot through 10 screens, commenced 
* If 120 feet be tbe distance of one screen from another, and the cubic 
law of resistance be applied, the actual time occupied by a 1 2 lbs. Armstrong 
shot passing over the interval t = -000869520 x 120 + *000000042 x 120 x 120 
Next, the velocity will equal unity divided by a quantity represented by 
•000869520 + -000000042 x 120. In this case the resistance will vary as the 
cube of the velocity. 
When 4,000 resistances at 10 screens for 400 rounds have thus been cal- 
culated, further corrections are required for the height of the barometer and 
temperature, and in each case the weight of the shot has to be an element 
of the calculation. The Report represents about five years of spontaneous 
labour, of a nature which few would like to undertake. 
The system of successive differences to ascertain errors of observation 
requires the results to be supplemented with an elaborate process of interpo- 
lation, described in the Transactions of the Royal Society, 1868. 
