84 
SHORT NOTES ON PROFESSIONAL SUBJECTS. 
Tlie central (2 ft.) hole in the front face was charged with compressed gun¬ 
cotton pellets, 1*25 inches in diameter, weighing 6’5 oz., and filling a length of 
about 9 inches of the hole. The other four holes in this face were each charged with 
4 oz. of gun-cotton pellets. The lateral holes received each a charge of 8 oz. 
The total quantity of gun-cotton in the nine holes amounted therefore to 3 lbs. 
6*5 oz. Electric detonating fuzes were placed upon the upper ends of the 
charges, and the holes were loosely plugged with wood borings to keep the fuzes 
in position. 
The nine charges were then exploded simultaneously, whereupon the mortar 
swayed forwards and appeared about to fall, but although the entire rear part of 
the bed was at once permanently raised from the ground by the great pre¬ 
ponderance in front, the mortar came to rest almost directly and remained firmly 
standing. 
The front face of the mortar bed had been to a great extent blown away and the 
wood composing it, and the portion of the bed beneath the trunnion block was 
completely disintegrated, but the enormous mass of metal resting upon this point 
caused the trunnion block to sink into and become firmly imbedded in the broken 
up wood, before the retaining power of the rear-fastening was overcome by the 
tilting forwards of the mortar. The latter seemed, therefore, to remain almost as 
firmly fixed as it originally was, but it appeared as if the equilibrium of the mass 
were in great measure maintained by the rear connexion of the mortar with the 
bed, through the agency of the keep-screw and bolt above described. It conse¬ 
quently was considered possible that, if this bolt could be broken, the relief of the 
mortar from its rear fastening might cause it to fall over. A disc of compressed 
gun-cotton, quite freely exposed, weighing 1 lb., with an electric detonating fuze 
attached, was therefore tied to the lower side of the iron joint, which connected 
the keep screw with the bolt. Its explosion, which was attended by a report 
like that produced by a heavy gun, snapped the iron joint in two, and also broke 
the wrought-iron bolt just where it entered the bed, so that it fell away from its 
fastening at the base of the bed. The mortar again moved forwards slightly, and 
the rear end of the bed was lifted still further, but the mass continued standing. 
It was now evident that the mortar was prevented from falling by the very firm 
manner in which its trunnion block had become imbedded in the soft self-padding 
debris of rotten wood, which was greatly aided, in the support it afforded, by the 
bolts on either side of each trunnion, which passed through the entire depth (3 ft.) 
of the bed at that part, and were nutted against iron plates let into its base. One 
trunnion had sunk considerably deeper into the wood than the other, and advantage 
was taken of cavities produced by the first explosion in that side of the bed, close 
to the bolts described, to place a disc of gun-cotton, weighing 1 lb., immediately 
under each side of this trunnion and close to each bolt. It was hoped that the 
simultaneous explosion of these two discs would lift the trunnion, and also destroy 
the support afforded by the bolts, either by snapping or drawing them. At the 
same time, with the view of aiding the effect of this explosion by simultaneously 
bringing an impetus to bear upon the rear portion of the mass, a 1 lb. disc of gun¬ 
cotton was inserted between the breech of the mortar and the cavity in the bed 
originally intended to receive it, but from which it had parted by the forward 
tilting of the mortar. The result of the simultaneous explosion of these three 
charges showed that a correct estimate had been formed of their effect. The 
mortar swayed for an instant or two and then fell slowly forward upon its muzzle. 
