Doe CAUSES OF DRIFT. 
The twist of the rifling in the 32-pr. gun, rifled on the Whitworth 
system, and with the intention of firing flat-headed shot, as being 
supposed more effective for penetration of iron plates than pointed shot, 
was much sharper than that of the 40-pr. Armstrong gun used for my 
own experiments; the left deflections given by the former were con- 
siderable and uniformly to the left (page 226). I was, however, only 
too glad to take the gun offered me, as there were no service guns then 
with a sharper twist. 
It is evident that the drift to the left of flat-headed shot fired with 
right-handed rotation proved conclusively that the cause assigned by 
Professor Magnus for the drift of projectiles, fired from rifled guns 
with high velocities is at least the chief cause, the so called rolling 
effect not being sufficient to counteract this left deflection. 
I will now give particulars of the attempt made to discredit the 
explanation of the cause of the drift given by Professor Magnus, and 
of the results of experiments described above, confirming it with 
respect to the deflection of flat-headed shot. 
On the 16th April, 1873, the following paragraph appeared in the 
Pall Mall Gazette :—“ But Colonel Owen, in ‘ Modern Artillery,’ states 
that flat-headed shot, under similar conditions, deviate in the opposite 
direction—that is, to the left. Though this theory has apparently been 
proved to be mathematically correct by Professor Bashforth, in his 
treatise ‘On the Motion of Projectiles,’ still it has not been generally 
accepted by artillerists ; and to test it, some flat-headed projectiles have 
been fired from the ten-inch howitzer. This piece was chosen on 
account of the very rapid twist of its rifling, and consequently great 
deviation of its projectiles; and it is found that all shot, whether flat 
or round-headed, deviate in the direction of their rotation.” 
Upon this paragraph I remarked* :—“ Why Professor Bashforth 
should be thus dragged in, considering he has made no special study of 
the subject, and merely makes a few remarks on what others have done 
is not very apparent.” 
Had the writer read the remarks on the subject in “ Modern 
Artillery,” or in Professor Magnus’ own work, he would have known 
that the theory was due to Professor Magnus, not Professor Bashforth ; 
and its practical confirmation to my own experiments, and that with 
the Whitworth gun, obtained from the records of older experiments. 
With regard to the experiments with the 10-inch howitzer, I re- 
markedt :—‘“ Against these forty or fifty rounds fired with great care, 
so as to obtain trustworthy results, the correspondent’s ‘all shot, 
whether flat or round-headed,’ only include three flat-headed shot, and 
these were fired with a very small charge (about one-fortieth), and 
therefore experienced a comparatively low resistance ; and at an angle 
of forty degrees of elevation, giving very long time of flight, and 
probably causing the resultant ‘of the air *s resistance to act on the body, 
below the head, “which would thus give a deflection to the right.” 
I did not know at the time that the so called flat-headed “shot were 
uot true cylinders; the point was flattened, but the corners were 
rounded. I will, however, allude to this again after giving the next 
* Appendix V., “ Modern Artillery.” 
+ The writer of the article confessed to me that he had never heard of this with the 
Whitworth gun. 
{ Appendix V., “Modern Artillery.” 
