Besides these there are two ranges of two tanks each, planted opposite the battery at Chaffin's Bluff. When they were planted it was not known that a battery was to be erected below. These four tanks contain about 6,000 pounds of powder. The great freshets of last month carried away the wires that were to operate the first pair. Lieut. Davidson, who, with the "Teaser" and her crew, has assisted me with the most hearty good will, has dragged for the tanks, but without success, they rest on the bottom. Could they be found it was my intention to raise the four, examine them and if in good condition, place them lower down. Lieut. Wm. L. Maury, assisted by Acting Master W. F. Carter, and R. Rollins, was charged with the duty of proving the tanks and packing them in casks. There are eleven others, each containing 70 pounds of powder. When tested in the barrels and found ready for use, they will be held in reserve in case of accident to those already down. A larger number was not prepared for want of powder. There are a quantity of admirably insulated wires, a number of shells for anchor or torpedoes and a sufficient quantity of chains for the wires remaining. They will be put in the navy store for safe keeping. The galvanic batteries, viz.: 21 Wollaston and one Cruickshank (the latter loaned by Dr. Maupin of the University of Virginia), with spare acids are at Chaffin's Bluff in charge of Acting Master Cheeney. He has also in pigs a sufficient quantity mixed to work the batteries, and ready to be poured in for use. It is proper that I should mention to the department, in terms of commendation the ready and valuable assistance afforded by Dr. Morris, president of the Telegraph Company, and his assistants, especially Mr. Goldwell. My duties in connection with those batteries being thus closed, I have the honor to await your further orders. Respectfully, etc., M. F. MAURY, Commander C. S. Navy. Hon. S. R. Mallory, Secretary of the Navy, Present. Shortly after, Captain Maury was ordered to London on secret service for the Navy Department, and that he might avail himself of laboratories and workshops for experiment and improvement of his new science, in which he was now regarded as supreme authority. He was to report progress and improvement in this new means of making successful war from time to time to the Navy Department, which was constantly done during the next two years, and thus the result of his labours and inventions communicated to the officers in charge of the torpedo stations now established along our Atlantic Coast. His devices and inventions, which have not since been surpassed and some of which are still in use, had reference chiefly to exploding the torpedo; to determining with certainty from a distance the moment when a ship should enter within explosive range, and at all times to test its condition and to verify its location.