THE BOYAL AETILLEEY INSTITUTION. 
217 
including six additional longitudinal bolts, at Mr. Mallet's suggestion. 
This would have doubled the longitudinal strength of the chase, and they 
would still have been about 13 ins. from centre to centre. The Committee, 
however, reported their opinion that no practical advantage to the public 
service was likely to be obtained by the continuation of the experiments. 
They expressed no opinion as to the interest or value of any theoretical 
results to be expected, and the Secretary of State decided to proceed no 
further. There was a probable reason assigned for the breaking of the tie. 
In driving in the new w r edges already referred to, the workmen extemporised 
a ram, slung from the loading crane; the position of the particular tie which 
broke was such that its wedges received a more direct and therefore more 
violent blow than any of the others, and it was probably overstrained. The 
effect was analogous to what has been since observed on some occasions 
from overstraining armour-bolts in screwing home the nuts. 
17. With regard to the other 3'6-inch mortar, it was, after some interval 
of time, put together in the Boyal Arsenal, of which it still forms one of 
the most conspicuous objects. It has never been fired. 
18. I have said nothing of the service of the mortar, or of various 
minor mishaps that befel the bed and platform. The latter are quite unim¬ 
portant. The platform, as before stated, had a slope of 12°, and the mortar 
recoiled on it 15 ins. with the largest charge. The momentum of so great 
a mass naturally tried all attachments, and some of them proved insufficiently 
strong, the cardinal rule of providing at first strength in excess, having been, 
as it so frequently is, neglected. The entire detachment detailed on the 
second occasion amounted to four non-commissioned officers and twenty 
gunners, who were able to load and fire about four shells per hour. 
19. The platform was destined, however, to be heard of again; for it had 
fallen into such a state of decay by 1869, that it was thought necessary by 
the Control Department to take some steps to prevent its giving way under 
the mortar. It is not so obvious what harm would have happened in that 
event; but “ as it would have entailed considerable expense to dismount the 
mortar, and then to remount it on a new bed and platform, it was decided 
to destroy the decayed bed by means of a small charge of gun-cotton, and 
thus allow the mortar to subside on to the ground." “The mortar” (after 
a discharge of gun-cotton) “swayed for an instant or two, and then fell 
slowly forward on its muzzle. The great feature of novelty connected with 
this operation was the accomplishment of great mechanical work by per¬ 
fectly unconfined gun-cotton, the force of which was instantaneously 
developed through the agency of a small initiative detonation. The total 
amount of gun-cotton used in the operation was 7 lbs. 6*5 ozs., the cost of 
which was ]2s. lOd.” - * Whether the mortar is injured or not, is unknown 
to the writer. The operation was attended with the complete destruction of 
valuable iron work connected with the bed. 
20. It will have been noticed in Table II. that the 19 shells fired are to 
be distributed in three classes—as heavy, medium, and light—and do not 
vary in weight within those classes more than about per cent. The 
ballistic coefficient C for each class is as follows :— 
See a fuller account, " Short Notes,” No. 62, p. 83. 1869. 
