105 
G U N. 
the diftance of feven hundred and fixty yards, it fome- 
times threw the ball one hundred yards to the right, 
and at other times one hundred to the left, of the line 
it was pointed in. The direction upwards and down¬ 
wards alfo was found equally uncertain, the ball fome- 
tinies bending fo much downwards as to fall two hun¬ 
dred yards fltort of its range at other times. Yet’the 
niced examination could not difcover that the barrel 
had darted in the lead from the pofition in which it was 
firft fixed. 
It is impoffible to fit a ball fo accurately to any plain 
piece, but that it will rub more againd one fide of the 
barrel than another, in its paflage through it. What¬ 
ever fide, therefore, it rubs againd on its quitting the 
muzzle, it will acquire a whirling motion towards that 
lide, and will be found to bend the line of its flight in 
the fame direction, whether it be to the right or the 
left, upwards, downwards, or obliquely. This deflec¬ 
tion from a draight line, arifes from the red da nee which 
the air gives to the flight of the bullet, it being greated 
on that fide where the whirling niption confpires with 
the progreflive one, and lead on that fide where it is 
oppofed to it: thus, if the ball in its paflage out rubs 
againd the left fide of the barrel, it will whirl towards 
that fide; and, as the right fide of the ball will there¬ 
fore turn up againd the air during its flight, the refid.. 
ance of the air will become greated on the right fide, 
and the ball be forced away to the left, which was the 
direction it whirled in. If the axis, round which the 
ball whirls, preferved its pofition during the whole of 
the flight, the deflection would be in the lame direction 
from the one end of the track to the .other. But, from 
accidents that are unavoidable, the axis of the whirl 
frequently changes its pofition feveral times during the 
flight; fo that the ball, indead of bending its coiirfe 
uniformly in the fame direction, often deferibes a track 
that is varioufly contorted. So great, however, is the 
tendency of the bail to defleCt itfelf towards the fide 
it rubs againd, that although, when fired out of a bar- ' 
rel that is bent towards the left hand, it will be thrown 
from the piece in the diredtion of the bend, yet as the 
ball in this cafe will be forced to rub againd the right 
fide of the muzzle, and thus turn its left fide up againd 
the air ; fo it will be found to alter its courfe during 
the flight, and bend away towards the right hand, fo as 
to fall a confiderable way to the right of the line in 
which the piece was pointed. 
From what has been firid, it will readily appear that 
thefe variations will be more frequent and confiderable 
when the ball runs very loofe in the piece, or w hen, 
from any rodghxiefs on its furface, or on the infide of 
the barrel, a confiderable degree of fridtion takes place 
between them. With a view to prevent fridtion, it has 
been propofed to greafe the ball ; but this will be of 
little fervice. All that can be done in a plain barrel, 
is, to have the balls cad very folid and true, and after¬ 
wards milled in the fame manner as is now pradtifed 
upon /hot: the barrel alfo lhould be very fmooth on 
the infide, and the ball fit it very accurately, fo as to 
leave fparcely any windage. And yet with the help of 
all thefe, it will dill be very difficult to prevent it alto¬ 
gether ; for gravity will condantly aft, and fridtion on 
tire under fide will naturally be occafioned by tiie weight 
of the ball. 
From confidering the caufes of this aberration in the 
flight of bullets, it will be pretty evident, that the only 
means of correcting it is by preventing the ball from 
rubbing more againd one fide of the barrel than another 
in palling through it ; and by giving to the bullet a 
motion, which will counteract every accidental one, 
and preferve its diredtion by making the refiflance of the 
air upon its fore part continue the fame in every part 
of the flight. The contrivance for this purpofe is 
termed rifling, and confifts in forming, upon the infide 
of the barrel, a number of furrows either in a draight 
Vol.IX. N0.569. 
or fpiral diredtion ; into thefe the ball is moulded, and 
any rolling motion along the Tides of the barrel, in its 
paflage out, thereby prevented. Barrels of this con- 
drudlion have been in ufe upon the continent fince the 
middle of the fixteenth century, but were little known, 
and dill lefs employed, in England, until after the 
commencement of the American war. The fpiral rifled 
barrels,-however, have entirely fuperceded the draight 
rifled ones, becaufe, although the latter prevented the 
rolling motion of the ball that takes place in a plain 
barrel, yet they do not communicate any other motion 
that could ferve to correCt the variations that may oc¬ 
cur during the flight. 
Thefurrows, or channels, which are termed the rifles, 
vary in number according to the fancy of the workman, 
or that of the purchafer, but are never lefs than fix, 
or more than twelve, in a comraon-fized piece. Their 
depth is equally fiibjeCt to variation; but the breadth 
of the furrows and of the threads is generally the fame. 
In fome pieces, the fpirals make a half turn, in others 
three-fourths, and in others, again, an entire revolution 
in the length, of the barrel : an entire revolution, how¬ 
ever, is the mod common ; though, from the great dif¬ 
ference in the length of rifle barrels, there fliould be 
fome dandard alligned for the obliquity of the fpiral. 
There is, without doubt, a certain obliquity of the fpi¬ 
ral which would communicate a rotary motion to the 
ball, fufficient to. corredt any aberration in its flight; 
and this might be determined by comparing the effects 
of a number of pieces, that differed only in the obli¬ 
quity of the rifles. Barrels intended to be rifled are 
previoufly bored and fmoothed within, in the manner 
already deferibed : they are, however, forged as much 
thicker than plain barrels as the depth of the rifles ; 
for, although the threads of the fpiral add to the 
weight of the barrel, they do not increafe its drengih 
in the lead, with regard to the force exerted upon it by 
the powder. 
Thefe pieces are charged in various ways. In gene¬ 
ral, the ball, which is fomewhat larger than the caiiber 
before it was rifled, is driven down to the powder, by 
means of an iron rammer, druck with a mallet, whereby 
that zone of the ball which is in contact with the Tides 
of the barrel, becomes indented allround, and is mould¬ 
ed to the form of the rifles. When the piece is fired, 
the projections of the ball which fill the rifles, being 
obliged to follow the fweep of the fpiral, the ball 
thereby acquires a rotary motion upon an axis that cor- 
refponds with the line of its direction ; fo that the fide 
of the bullet which lay foremod in the barrel, conti¬ 
nues foremod during the whole of the flight. By this 
means the refiflance of the air is oppofed direCtly to the 
bullet’s progrefs, and not ekerted more againd one part 
than another of that fide which moves foremod; and 
accordingly the bullet preferves the line of its direction 
with very great deadinefs. 
It appears, that neither the inventors of fpiral rifle 
barrels, nor the perfons whofird ufed them, were at all 
acquainted with the principles upon which they pro¬ 
duced their effects. Some were of opinion, that, owing 
to the ball not pafling out fo quickly as from a plain 
barrel, the powder was more completely inflamed, and 
thereby exerted a greater force upon it. Others, and 
thefe by far the greater number, thought that the ball, 
by combining the rotary with the progreflive motion, 
did, as it were, bore the air ; thereby flying much far¬ 
ther, and penetrating folid bodies to a greater depth; 
than when difeharged from a plain barrel. But Mr. 
Robins afferts, that, as the bullet meets with a.greater 
refiflance in its paflage through a rifled barrel than 
through a plain one ; fo that neither its velocity, nor the 
didance to which it is thrown, is fo great when fired 
from the former as when fired from the latter : and this 
difference will be very remarkable if the rifles be deep, 
and the ball fills them up completely ; the friftion, in 
E e that 
