39£ 
MINUTES OF PROCEEDINGS OF 
Taking a 600-pr. gun and high pressures, we should, under the same 
conditions as before, have with the Whitworth rifling about 700 tons pro¬ 
ducing rotation, which would be more than 100 tons on each edge; and if 
we suppose the driving edge to be 1 in. wide* and 20 ins. long, it would, 
with 1 turn in 40 calibres, give a pressure of 5 tons per square inch, 
which, on the great amount of surface employed, must produce enormous 
friction. With a 1200-pr. it would be worse and worse—about 8 tons 
per square inch on a still greater surface. Still worse, however, Whit¬ 
worth's small bore necessitates a twist of 1 turn in 20‘calibres; so that 
these pressures, great as they are, would have to be doubled. It is 
difficult to estimate the amount of longitudinal pressure that would thus 
be consumed; the co-efficient of friction with such high pressures 
being very great. Probably it would not be less than 10 per cent. 
Captain Scott's system, having less bearing surface, but acting at 
the end of the radius, will probably, with the same twist and number 
of grooves,! have about the same amount of pressure per square inch 
as Whitworth's system, but will impede the velocity of the projectile 
less, owing to the smaller amount of surface under friction. The number 
of his grooves, however, can be increased to any amount, and thus the 
friction can be reduced to any extent desirable—a point of very great 
importance, as there is a limit, by the laws of practical mechanics, to 
the amount of pressure which should be given between surfaces in 
contact—700 lbs. per square inch. 
With lead-coated projectiles, the whole surface would probably be 
under the action of friction to produce rotation; but, owing to the 
softness of the lead, and the difficulty of securing its proper adhesion 
to the body of the shot, it is hard to form any estimate of its value 
with very heavy guns. The longitudinal friction of the lead-coating 
in the bore is enormous, wasting on an average, with very heavy guns, 
about 10 per cent, of the useful effect of the gas—no other system, 
except Whitworth's, wasting nearly the same amount of the longitudinal 
pressure forward. 
The Norwegian system is less capable of giving effective rotation. 
The number of the driving studs could, however, easily be increased. 
But, instead of this, the rotation is diminished, giving only 1 turn in 55 
calibres; and with large bores and tolerable centring very good shooting 
is obtained. 
Excepting, perhaps, lead-coated projectiles, the Woolwich studs are 
strained most severely, and are often subjected to a strain of probably 
20 tons per square inch, causing the studs to bulge. An extra stud, 
* Whitworth claims a greater breadth of bearing surface than is here stated, but it is questionable 
if he gets more; because the pressure is obtained by the yielding of the metal to some extent, and 
this can scarcely be allowed for. Besides, any additional surface brought into play will act at 
shorter radius, and produce less proportionate effect in giving rotation, but more in giving friction. 
f The grooves, however, are here supposed to be deeper than those used by Captain Scott in his 
guns of smaller calibre, which are only -125 in. deep. It is not necessary to consider the depth of 
Captain Scott’s grooves an essential element of his system, any more than the number. As the 
number increases, so may the depth without detriment. Whitworth, however, cannot increase the 
number of his grooves. 
