511 TRANSACTIONS OP THE AMERICAN INSTITUTE. 



vessel, bj drawing tlie sand through a tube sunk to the bottom 

 of the water, in which case the sand need not be raised at all. 



Mr. Johnson. — It was suggested a few years ago to make 

 an island of five acres, for hospital purposes. There were six 

 feet of water, and it was estimated that 1GY,000 cubic yards 

 of sand would be required. I made a rough estimate at the 

 time that it would take about thirty days to do that with a 

 moderate amount of power, moving the sand for one-third of a 

 mile. 



Mr. Fisher. — There is a current over most bars. If the sand 

 were mixed w'ith water would not most of it go off to sea ? 



Mr. Johnson. — It would not go very far. Mud would remain 

 longer in suspension than sand. 



BLOCKADING. 



Mr. C. W. Smith. — "We all know what uncomfortable .things 

 snags are. I see no reason why we should not drive piles ten or 

 twenty feet apart ; perhaps at such an angle as to present their 

 points outward to catch into any vessel which might seek to come 

 up. It seems to me that there is no other way for obstructing a 

 harbor, so cheap and feasible as that. No vessel, unless iron-clad, 

 could force its w^ay through. 



Mr. Dibben. — I would respectfully submit that we have some- 

 thing else for our navy to do besides watching these entrances, 

 and I consider the obstructing of some of these inlets, so as to 

 allow one vessel to do the w^ork of two or three, a credit to him 

 that devised it. But this bugbear story of spoiling harbors is 

 all a humbug. Charleston harbor can be restored to its former 

 condition for $10,000. You may do all you can for six months 

 to spoil Charleston harbor, and I will guaranty to make it better 

 than it was before for $50,000. Sand can be moved very easily, 

 and stones still more easily. Bring up a lighter alongside, hook 

 on to a stone and hoist it up with a little engine, and hook on to 

 another one, and as soon as the stones are out the old hulk will 

 float. And the entrance will be better after the obstructions are 

 removed than it was before, because it can be made of a syste- 

 matic width. 



Mr. Fisher. — The plan of obstructing harbors, by driving piles, 

 strikes me very favorably. 



Mr. Selleck. — I have seen piles driven 200 feet deep, placing 

 one upon the top of another. They can be driven in w^ater of 

 any depth. 



