A gentleman direct trom Jalt;niore, and wlio bas secn the atcam-gun (about whicli considerable Ihu been said) opérate, lias furnislied us with the following deseriptiim of it . It is on lour wliculs ; llie boilcf is lilto' tliat of an ordinary stearn fireengine, tha cjlinder being upright. There is but, oue barrel, which is of steel, on a pivot, and othenvise is like an onhnary niusket barrel. It is fedor loaded throngli a hopper entering thci barrel directly over llie pivot. The barrel has a rotary motioii, and pcrforni the cireumference, by ma cliinery attached, at the rate of ibaM gilteeu hundred times a minute. 'ÍKü baila aro let into the barrel through a vahe at WÍll, and every time ■ the barrel comes round to a certaiu point, anothur valve, self-operated, Iets out a ball, wlnqli. is propelled solely by the vcloeity of tbe barrel" in revolwug. ■ ' '! It wfll discharge a two ounce ball throe hundred times a minute. The range is accurate up and down, but thvballs are liable to hit ide of the mark on one side or the other. The barrel rces inside of a drum, made of bti'tf' iron, betwein öve and six feet in cireumferencpj witli titt Opening where the balls are discharged. lts range is not over. one hundred yards at best, and the gurx can be worked so as to discharge in iiUy. direction. The whole thing weigha ti,700 lbs., and is about the size of a steam fire engine. It is the opinión of our informant that the gun does not warrant the expectations of the inventor, and that it is not likelv to be of much service. - '