246 
POPULAR. SCIENCE REVIEW. 
and the rifling consists of eleven grooves in the bore at a spiral 
increasing from nothing, or the direct direction, at the bottom 
of the bore to one turn in 35 calibres at the muzzle. The 
projectiles have three gun-metal studs for each groove. The 
weight of the projectile, when the bore of the gun is of its full 
dimensions, may be about 1,600 lbs., and that of the charge 
300 lbs., with a muzzle velocity of about 1,400 feet per 
second. 
The question of the carriage is an interesting one. It was clearly 
desirable to find some way of facilitating the operations of mov- 
ing this gun about. Light guns travel on their firing carriages. 
Heavy guns are generally conveyed entirely separate from their 
carriages. Indeed their carriages are massive frames of iron, 
supplied only with small trucks, which are brought into play by 
hydraulic lifts when the carriage is to run up a few feet along 
its platform. The carriage and gun are separately lifted by 
cranes, sheers, gins, and the like ; and by the same means the 
gun is placed on its carriage when mounted, and lifted off and 
lowered when dismounted. These operations are slow, and such 
as need much mechanical apparatus, and considerable skill to 
carry out with safety to those engaged in them, because with 
exceptionally heavy weights the strain likely to be brought on 
every part of the gear must be carefully calculated. A weight 
of 80 tons would be so greatly in excess of any that has 
hitherto been dealt with, that a special supply of apparatus 
might have to he made to any place where the gun was to be 
moved and mounted. Even at. the Royal Arsenal the great 
hydraulic crane, which was hitherto found able to seize up and 
swing round any desired weight as if it were playing with it, 
had to be strengthened. The operations of loading and unload- 
ing, mounting and dismounting, could not fail to involve con- 
siderable expense and difficulty at out-stations. Under these 
circumstances the idea was suggested of dispensing with them 
by building a carriage on which the gun might both fire and 
travel ; in fact, to make the monster approach in its conditions 
to a field piece — with this exception, that its movement was 
always to he on railway lines, for which purpose the carriage 
must be made to suit the narrow gauge. Whether this idea 
originated with the Royal Carriage Department or with Major 
Maitland of the Grun Factories, it may be hard to say ; at all 
events it is to he highly commended. 
The carrying out of it was, however, by no means easy, and 
Colonel Field and Mr. Butter are to he congratulated on their 
complete success. To understand the difficulties, the action of 
a gun in firing must he considered. The carriage is driven 
hack by a violent force applied at the bottom of the bore of the 
gun. The recoil is then checked gradually by brakes applied 
