Page:Brief Sketch of Work of Matthew Fontaine Maury 1861-65.pdf/16

 They are arranged in rows, as per diagram, those of each row being thirty feet apart. Each tank is contained in a water-tight wooden cask, capable of floating but anchored, and held below the surface from three to eight feet, according to the state of the tide. The anchor to each is an eighteen inch shell and a piece of kentledge so placed as to prevent the barrels from fouling the buoy ropes at the change of the tide. Each shell of a row is connected with the next one to it by a stout rope thirty feet long, and capable of lifting it in case the cask be carried away. The casks are water-tight, as are also the tanks, the electric cord entering and returning through the same head. The wire for the return current from the battery is passed from shell to shell and along the connecting rope, which lies at the bottom.

The wire that passes from cask to cask is stopped aslack to the buoy rope from the shell up to the cask to which it is securely seized, to prevent any strain upon that part which enters the cask. The return wire is stopped in like manner down the buoy ropes to the shell, and then along the span to the next shell. At 4 the two cords are rapped together, loaded with trace chains a fathom apart and carried ashore to the galvanic battery. For batteries we have 21 Wollastons, each trough containing 18 pairs of plates, zinc and wire, 10 x 12 inches. The first range is called 1: the second 2: the third 3, and the wires are so labelled. Thus all of each range are exploded at once.

Besides these there are two ranges of two tanks each, planted opposite the battery at Chaffins 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