1879.] on the ' Tlinndcrer ' Gun Exjylosion. 247 



to depend on, but lias also the support of the metal on cacli side of 

 it, wliicli metal at the sides is not similarly strained. Obviously tlio 

 metal in advance of the base of the shot is not exposed to pressure 

 at all. I wish time admitted of my describing to you certain 

 experiments I made as long back as the year 1870 on the " Contrc- 

 vapeur" break, in which I succeeded in obtaining by this ram 

 principle a much higher pressure of steam in the cylinders of a 

 locomotive enujino than was at the time prevailing in the boiler ; 

 but I must content myself by referring those who may be interested 

 in pursuing this subject to the volume for the year 1870 of the 

 * Transactions of the Institution of Mechanical Engineers.' 



Further, with regard to this question of air space, it is well known 

 that a sporting gun may be burst by the muzzle being choked with 

 snow or with dirt when it is fired. The explanation of this is simple. 

 The bullet, at the time it reaches the neighbourhood of the muzzle, 

 has attained great velocity, and the pressure required to set even such 

 light weights as snow or a little earth practically instantaneously into 

 motion as rapid as that of the bullet, is sufficient to force these 

 materials out sideways, and to produce a burst in the same way as 

 the resistance offered by water to the setting up of sudden great 

 velocity is sufficient to cause a shot to ricochet. 



The best illustration of the way in which a bullet striking a soft 

 obstacle near the muzzle, would act on that obstacle is, probably, 

 to imagine a diaphragm of water extended across the barrel of a 

 musket. One then has no difficulty in seeing that the intense pressure 

 set up on such a diaphragm must be communicated to the side of the 

 barrel. Again, in a musket the bulging may be due to the expansion 

 of the projectile itself when striking a foreign object j^laced in its 

 way. And I may tell you that Captain Noble has experimented, by 

 putting a wax wad near the muzzle of a musket, the wad being equal 

 in weight to the projectile itself, and that on firing, this obstacle was 

 exj^anded and bulged, and sj^lit the barrel. He then placed the pro- 

 jectile near the muzzle, and fired the wax wad: a similar result 

 ensued. Finally, on this subject I will ask your attention to 

 Diagram 18, which shows the experiments as to air spaces made by 

 Captain Noble in a 10-inch gun, having a 12-inch powder chamber, 

 and with the following results : — 



The powder used in the first experiment was pebble powder, and 

 occupying such a space as would give a pressure of about 20 tons to 

 the square inch, and would impart to a 400-lb. projectile a muzzle 

 velocity of 1487 feet per second. A crusher gauge was placed in the 

 bottom of the bore of the gun, and three such gauges were fixed in 

 the base of the projectile ; one as near as possible to its toj^, one in its 

 centre, and one near the bottom ; these gauges had been previously 

 compressed so as not to move unless a pressure exceeding 10 tons per 

 square inch came upon them. The projectile was placed 2 feet 

 away from the cartridge, that is to say, there was a 2-feet air sjiace ; 

 as the result, the velocity was only 1240 feet per second instead of the 



