The Situation before Atlanta.

The St. Louis Union publishes the following interesting letter received by a gentleman in that city from a relative, who is an officer occupying an important position in Gen. Sherman's army. The letter bears date "In Front of Atlanta, July 25th, 1864." It will thus be seen that it was written before the affair of the 28th, in which the rebels are reported to have lost 4,000 more in their desperate but futile efforts to break through Gen. Sherman's line:

"We are in the immediate front of Atlanta, with the enemy well nigh shut up in its very defences. We occupy a curved line around the west, north and east sides of the city, about one to one and a half miles distant from it, and have the whole place under the fire of our guns, to doses of which, anything but homeopathic, we have been treating it during the past forty-eight hours. We have fought some half dozen battles, and, with losses to ourselves (in all) of about 12,000 to 15,000, have placed of the enemy at least 30,000 hors du combat. We have captured twenty guns, twenty five or thirty stand of colors, have destroyed two important railroads, occupying a third for our own uses; haye burned a large number of valuable cotton, woolen, rolling, paper and grist mills, nearly 3,000 bales of cotton, numerous railroad depots, and large quantities of subsistence and other military stores. We have captured thousands of horses, mules, beef cattle and sheep; and have sent to the rear nearly 10,000 prisoners. I place Jo. Johnston's loss at 30,000 because, besides the above prisoners, we have either buried or delivered up to him for burial, about 5,000 of his dead. Counting five wounded to one dead (which is a moderate proportion) and I think you will agree that I do not overestimate his entire loss. Unless some unforeseen accident or misfortune overtakes us, Atlanta will be ours very shortly."