302 NEW FIELD CARRIAGE (IRON) FOR LONG-RANGE GUNS. 
replacing the large transom of the ordinary trail by a narrow trail end, 
embracing above and below the brackets, of which it strengthens the 
connection at this point in a most efficient way. It prevents one of 
the brackets only being subjected to any shock whatever; it transmits 
it to both at once. 
These different improvements increase the intrinsic strength of the 
carriage, but in no way modify the effects of the gun upon it. The 
intensity of these effects, as we have seen above, can be expressed by 
i ( m + %) v2 
{n + 1) m' 3 
and depend on the magnitude of n —that is to say, on the relation 
between the weight of the gun and that of the carriage. 
Consequently, in order to obtain a sensible diminution of the destruc¬ 
tive effects of the gun on the carriage, it will be necessary to reduce 
largely the weight of the latter ; but as the gun-carriage is at the same 
time a travelling carriage, into the construction of which there enter 
wheels, axletree, and seats, the weight of which we cannot lessen, it 
becomes practically impossible to lighten the carriage. We can, how¬ 
ever, lessen the destructive effects of the gun if we divide the 
carriage into two distinct parts—the carriage properly so called as one 
part, and the axletree, with wheels and seats, as the other. 
This division is effected in the following way. The axletree, in place 
of being housed in the brackets, can slide backwards and forwards 
within the straps which unite it to them. At the inner ends of the 
axletree-arms it is held by two tie-bars, which are united to each other 
at their other, ends by a collar-bolt, square in section. In the same 
way as the axletree, this collar-bolt can move in a 'slot cut for this 
purpose in the brackets. The collar-bolt, tie-bars, and axletree form 
thus a frame upon which are fixed the axletree-seats. This frame 
placed upon wheels constitutes one part of the carriage. 
This part is connected with the trail by means of two bolts with pierced 
heads, hh (see Plate, Pigs. 2 and 3), fixed to the square collar-bolt, 
These bolts pass through the transom, cc, and the iron plate, gg, between 
which are placed several thicknesses of cork. The cork is now replaced 
by india-rubber, which is more durable. This modification is applied 
to carriages of recent construction. The threaded ends of the bolts, M, 
are furnished with screwed nuts, whose play compresses the india-rubber 
and exercises a force on the collar-bolt, ff 3 and consequently on the axle- 
tree, towards the transom, cc. The axletree is thus pulled back until it 
takes a bearing against the rear side of the straps which unite it to the 
bracket. 
The layers of india-rubber interposed form an elastic buffer, the thick¬ 
ness of which is reduced from 7'1 ins. to 3*59 ins. by the screwing up 
of the nuts. It is then under a pressure of about 4 tons 16 cwt., as we 
can see from the following table, which shows the thickness of the 
buffer under various pressures, measured from direct experiment, the 
section of the buffer being about 45 sq. ins. 
