CAUSES OF DRIFT. 239 
I have an entire disbelief in any study of this subject which in the 
main is not on experimental lines. So many factors enter into the case, 
and so many. brilliant mathematical intellects have given their attention 
to the subject with very small result, that I am sure what we want to 
know principally are facts, and then you may trust the mathematicians 
to fit the theory to the facts. In the present state of science it seems 
almost incredible that so much should be a matter of conjecture. That 
is all I have to say. (Loud applause.) 
MaAJor G. MACKINLAY, (late) R.A.—As the Text Book of Gunnery has 
been alluded to, I would mention that it is intended to be confined to 
that which can be proved by well-established facts. As itis a text book, 
‘speculations and mere theories are avoided as much as possible ; gyros- 
copic action (to which, I believe, drift is chiefly due) is explained at 
some length in a couple of pages (242-244). 
The present occasion, however, is one when less guarded language is 
permissible and when any theory may be discussed. 
I think the lecturer has most successfully proved from the results of 
actual experiment the fallacy of the old hasty generalization, that all 
projectiles drift in the direction in which they rotate; as he has given 
good evidence that some flat-headed projectiles with right-handed rota- 
tion drift to the left. We must not however run away with the idea 
that ali flat-headed projectiles will behave in the same manner; the 
lecturer has himself indicated that the centre of resistance would 
probably act, even with flat-headed projectiles, on opposite sides of the 
centre of gravity with long and with short shells, thus causing corres- 
ponding drift to the right or to the left. Doubtless, also, many other 
circumstances influence the position of the centre of pressure of the 
resisting air, such ag the distribution of the weight of shell, shape of its 
recis, roughness or smoothness of different parts of its surface, &., &e. 
The lecturer has pointed out that flat-headed projectiles are not well 
adapted for flight, as they require more rotation than pointed shells of 
about the same calibre and weight to keep them steady in their course ; 
as also the flat head offers an increased resistance to the air it is not 
likely that they will ever be used in the future, and the general ques- 
tion of the drift of flat-headed projectiles will probably not be decided 
by actual trial. 
With regard to Colonel Bainbridge’s interesting statement about the 
diminished drift of modern high-velocity projectiles, I notice in 
accordance with it that in the 8-in. Howitzer* fired with different 
charges the higher the muzzle velocity the less is always the drift, 
whether we compare equal ranges or equal times of flight. I should be 
inclined to attribute the diminished drift, under all these circumstances, 
to the higher velocity of rotation consequent on increased muzzle 
velocity. : 
In conclusion, I believe drift to be the result of a large number of 
causes, the principal being gyroscopic; the others are very little known 
except by their combined result. 
CAPTAIN J. H. MANSELL, R.A.—Sir, the lecturer has pointed out, as we 
have already been shown, what effect the gyroscopic action has on the 
ultimate drift of a projectile ; but there is one point that I am not at all 
clear about from what we have heard. The lecturer has told us that 
* See Range Table 8-in. R.M. Howitzer, p, 309 Text Book of Gunnery. 
