MEUTENANT LONGSTREET.The following account of til# gallantry of this young Georgian, wo find in the Charleston 3fcr-citry, extracted from a letter from an officer of the 2nd Dragoons, to a gontleinanin Charlestop?14 The South Carolina Regiment behaved with!' distinguished gallantry at Churubusco, and again at the storming of Ghapultepec. In the former they suffered terribly, losing one-tbird of tbeit number, and very severely also hi the latter, ao that now, out of tho nine hundred men, who composed the Regimet when h left Charleston, it can muster but about eighty or ninety. I should say; though that sickness at Puebla had reduced them more than half before weleft that city. S. Sumter Was Wounded at (jhurubuseo; but is rapidly regaining his health. I take great pleasure ia relating an account of an exploit of our friend Longstreet, who highly distinguished himself at the tete du pont at Clmrnbu6co. • This work was very strong, and its guns were served by the da-' sorters of our army, who fought with the energy of . despair, whilst a hail-storm of musket balls' poured upon our columns from all parts of tho parapet, from the fortified cjhuroh neair by,'and from the banks of the canaL This terrific fire drove back a regiment in confusion npon the 8th Infantry, (Longstreet’s,) and it also began to. waver, when L. seized the regimental colors, and accompanied by another officer, (Captain Romford) rushed forward, calling upon all brave men to follow their standard. * The men, cheered by this courageous act;rushed with a shout upon tho tetc da pont. Longstreet, still bearing the colora, ran ih advance of all to the very ditch of fho work; it was full of ^ water, but be plunged in, crossed it, and'climbing the cmbarkuiCnt, planted his standard on tho fort, which his bold act bad caused all to fly from, save the deserters, who fearing, if they ran, they would be Bbot by the Mexicans, stood their ground to tho last, and all of them (about eighty) were made prisoners.— L. was badly wounded in approaching the City on' the 13th, but bo is recovering rapidly. Hill was in tho storming party at chapultcpec, but came off unhurt. Thomas, Brown, Judd, and Austin* are safe and well. I was comcpletoly worn down before we entered tbe city. For the last month, in fact, ever since we left Puebla, it would net bo an exaggeration to say, that we havo been constantly 5n the saddle. ”