A Waste of Shells.Accounts from Charleston, (says the Augusta Constitutionalist,)state that for six hours the Yankees threw shells at our batteries at the rate of twenty per minute. At this rate seven thousand two hundred shells were fired during the time specified. The cost of a single shell in the United States, we believe, is $14. The expense of this pyrotechnic display would therefore amount to $100,000 in round numbers. Individual estimates of the number of projectiles thrown since the beginning of the seige will vary; but, with the almost incessant firing and the terrific bombardments of the 18th of July and other days that might be named, we think it safe to put it at 75,000—value $1,050,000. This is going deepinto the Yankee exchequer,but Johnathan still continues to “shell out”lavishly.It is said that the shells which are fired into the sand banks of battery Wagner are densely packed, and only serve to strengthen the works the more.