44 PROCEEDINGS OF THE 



E. Belcher thought that the reason the gun was not heated by an explosion of 

 gun-cotton miglit be because the gases had not time to heat the gun owing to the 

 rapidity of the explosion, which was slower in the case of gunpowder; or that it 

 might arise from the greater amount of fouling in the case of gunpowder. — Capt. 

 Maury said this Report was something more than interesting, because it was so 

 exceedingly suggestive ; and it appeared to him that it afforded them an element 

 of security by giving the preponderance on the side of defence. Ever since steam 

 had been applied to purposes of naval warfare it bad been considered a matter of 

 very great doubt by many professional men how far ordinary steamers and men- 

 of-war, where forts were to be passed at the mouth of a river, were capable of 

 sustaining the fire of such forts and passing up the river. And to show that there 

 was ample time for them to do so, they had only to recollect the fact of steamers 

 having fought forts for several hours. In the Crimea and at Charleston the 

 steamers had remained under fire for several hours — a much longer time than was 

 necessary to enable them to pass the forts and go higher up the river into a place 

 of safety where they could do damage to the enemy. Iron clads had rendered 

 this much more easy than it had previously been. If then their principal defences 

 failed them at the mouth of the river in this way, the question was whether they 

 should not have recourse to mining for the destruction of the invading vessels? 

 He himself had been engaged upon the subject. He found this difficulty in em- 

 ploying gunpowder, that in order to be sure of destroying the vessel as she passed 

 in a given line by means of gunpowder, the magazines must be in actual contact, 

 or very nearly in actual contact with the side of the vessel ; otherwise the pro- 

 bability was that the vessel would not be destroyed. Last week they had the 

 intelligence of a vessel having had a mine exploded under her on the James 

 River. That magazine contained several thousands of pounds of powder. The 

 vessel did not know that the mine was there ; but the mine did not destroy the 

 vessel. It merely threw up a column of water which washed some of the men 

 overboard. His own conclusion was that to make sure of destroying a vessel 

 after she had passed the forts, they must mine the channel in such a manner that 

 the vessel must come in contact with one or other of the mines. It was found 

 that wooden vessels to contain the powder would not do. They would not confine 

 the powder long enough to produce a sufficient foree. It was necessary to make 

 them of stout boiler iron. It would not do to leave the magazines on the top of 

 the water, and it would not do to put them at the bottom, for then there would be 

 a cushion of water between the bottom of the ship to be destroyed and the maga- 

 zine, which would protect the vessel. In short they had to anchor them beneath 

 the surface with short buoy-ropes, at a depth proportioned to the kind of vessel 

 expected to come up. But when they made the magazine of boiler-iron they had 

 to have buoys to float it so large that they were always in danger of being carried 

 away by the vessels crossing the line of magazine. The plan was to place those 

 magazines in a ring in such a position that the vessel in passing would have to 

 come in contact with at least one and probably two of them. It was necessary 

 to place those magazines of powder so that when you saw the vessel in that range 

 you had only to bring the two poles of the galvanic battery together and make 

 the explosion. There was, as already stated, a difficulty in usmg gunpowder. 

 But since gun-cotton had the remarkable effect of destroying a vessel — he did not 



