In some instances it may not be practicable to reach the enemy's ship or other object of attack directly from the station to which the torpedo boat is connected, and from which it is controlled. In this case a small boat, &c., is used in addition, which should be so arranged as to present to the enemy's view as slight a surface as possible. This mode of attack is shown at Fig. 138, where _A_ is the torpedo boat, and _N_ is the small auxiliary boat. This boat _N_ is provided with a keyboard and battery like that described at page 144, and the electric cable _L_, carried on and payed out from the torpedo boat _A_, is connected with the keyboard. The boat _N_ is also attached to and towed by the torpedo boat _A_ by the tow line _O_; and the torpedo boat is steered and guided by means of the said keyboard in the boat _N_. The auxiliary boat is designed to contain two men, who lie down, one at the bow, the other in any convenient position abaft him; the latter has control of the keyboard, while the former by the aid of a telescope keeps the torpedo boat in view, and transmits his orders to the man at the keyboard. On arriving at such a distance from the enemy as to render an attack practicable, the tow line _O_ is disengaged, and the torpedo boat _A_, guided and controlled, and fired from the boat _N_. The torpedo boat being exploded, the auxiliary boat can be rowed back to the station or ship to which it belongs. By this means the range of action of the torpedo boat is greatly extended, and with comparatively slight danger to those employed in making the attack. A more recent form of the Lay torpedo boat is shown at Figs. 139, 140, and 141, where Fig. 139 is a plan or top view of such a boat, Fig. 140 is a side elevation of the same, and Fig. 141 is a midship section on the line _x x_. _A_ is the hull of the boat, _a_ is the main or central portion of the said hull, _b_, _b_ are side or auxiliary portions of the same. These parts _a_ and _b_ may be oval or circular in transverse section; they are constructed of thin steel or other suitable sheet metal, and secured together by riveting or bolting. The side or auxiliary portion _b_ form the reservoirs or chambers for the gas; they also serve to contain the propelling engines. _c_ is the magazine, _d_ the chamber or compartment for containing the coiled cable, _e_ is the compartment containing the electrical steering and other apparatus, _f_ is the firing rod or pin, _g_ is the water ballast chamber, _h_ is the cable, _i_ the paying-out tube, _j_, _j_ are the screws or propellers which rotate in opposite directions, and _k_, _k_ are the sight or guiding rods. The parts of the apparatus or mechanism whereby the various operations of the torpedo boat are effected are connected to the cable and controlled by electric currents transmitted from the station through the cable, as previously described. The Lay torpedo boat weighs about 1 ton, its length is 23 feet, and speed 12 knots per hour.