A report has been recently received by the Corporation of Georgetown, D. C, from the distinguished engineer, Charles Ellet, Jr., Esq., on the much-talked-of scheme of a bridge across the Potomac near that town, at a spot called the Three Sisters, about half a mile west of the aqueduct. The bridge Mr. Ellet proposes is a wire suspension bridge, of such size and weight as to be competent to the uses of railroad as well as ordinary travel. At the preferred point, at the Three Sisters, the river is 1,030 feet wide, which would be the length of a bridge there. This distance Mr. Ellet proposes to span with a single arch, declining to use the granite rocks which lie in the river in the line of the proposed structure. The cost of this structure he sets down at $297 870, but says that if the bridge be divided into two spans by a pier on the aforesaid rocks, the cost would be only $240,000. He prefers the sigle span, however, on account of its handsomer appearance. This bridge, he states, would be four times heavier and stouter, and therefore tour times stronger, than the Wheeling suspension bridge (of which Mr. Ellet was constructor,) and would more than sustain the simultaneous pressure or weight of two locomotive engines with their tenders, forty loaded freight cars, one hundred loaded carts on the carriage-ways, and one hundred horses, enough to occupy the bridge from end to end, and in all amounting to six hundred tons weight.