RESISTANCE OF THE AIR TO RIFLED PROJECTILES. 
445 
The graphical method mentioned above was devised to evade the arithmetical diffi- 
culties of the question; and I hope shortly to be able to publish an account of it*. 
Colonel Halford has since been so obliging as to communicate to me the following 
notes of the experimental data. These are as follows : — 
“ The means by which the angles of Metford’s match-rifles were arrived, at. 
“ The rifles were shot at 12^ yards to get the zero on the tangent-scale. 
“ This distance is taken because, with a radius of 12^ yards, of an inch is one minute 
of angular space, an easy quantity to deal with. Corrections made for height of fore 
sight above axis of bore, and for fall of bullet, at 12^ yards, taken as one minute. 
“ The tangent-scale is then carefully cut for radius between the sights to read to 
minutes with a vernier. It can be read to 15" by careful inspection. The Table of 
angles is then made from careful registers of shooting in all weathers, but especially 
calm weather, at different distances, but chiefly at 200 yards, 500, 600, 800, 900, and 
1100 yards. Nine times out of ten the angles will be found to be perfectly correct in 
calm weather. Difference of barometrical pressure will make a slight difference. The 
Table furnished [i. e. of elevations corresponding to ranges] was drawn out by Mr. Metford, 
and has been very heavily tested by myself, and tallies exactly with my experience. The 
angles have been compared with those used by other men using similar rifles, and have 
been found to tally, making slight allowance for the little differences of speed which 
different barrels will give — usually not more than is due to 0° 2' of elevation in 1000' 
yards. I must have fired from 8000 to 9000 shots. I have most of my shots registered. 
I should say that the Tables have been worked out from results given by at least 30,000 
shots. 
Ranges. 
Elevations, 
Table No. i. 
Elevations, 
Table No. 2. 
Elevations, 
Table No. 3. 
Yards. 
100 
9 15 
9 30 
10 30 
200 
19 30 
20 
20 30 
300 
30 45 
31 30 
32 30 
400 
43 
44 
45 15 
500 
56 15 
57 30 
59 
600 
1 10 30 
1 12 
1 14 
700 
1 25 45 
1 27 30 
1 29 30 
800 
1 42 
1 44 
1 46 30 
900 
1 59 30 
2 1 30 
2 4 45 
1000 
2 17 30 
2 20 
2 23 
1100 
2 36 45 
2 39 30 
2 42 30 
“No. 3 Table is not perfect in itself ; it is a Table used occasionally with a head wind, 
and has not been so carefully worked out as the others ; a head wind is so disturbing- 
in its effects that, practically, it is almost impossible to verify it. The other Tables are 
reliable within very small fractions. 
* [This has since appeared in the Philosophical Magazine for June 1868.} 
