March 



22, i< 



)•] 



SCIENCE. 



213 



grees. When the inner tube is pushed right out, and the boat is 

 floating near the surface, only the top of the telescope tube need 

 be above the water ; and the captain, standing within the boat, by 

 glancing upward, can see in the mirror what is going on in front 

 of him, or, for the matter of that, all around him, if the inner tube 

 be revolved. By means of this ingenious application of a tele- 

 scopic conning-tower with a mirror, the size of that part of the 

 vessel which must project above the water-level to permit of an 

 observation being taken, has been much reduced, as compared 

 with the old plan of making the conning-tower large enough for 

 the captain's head and shoulders to enter. In the stem of the ves- 

 sel is fixed the torpedo-launching tube, and in the stern the electric 

 motor by which the propeller is driven. There are various water- 

 ballast tanks by which the vessel is trimmed, and access to the in- 



distance that the boat could travel with one charge would be about 

 120 knots. 



While the " Gymnote " is a boat mainly intended for the dis- 

 charge of torpedoes against the enemy's ships, a second and mucb 

 smaller submarine boat is now being built, the mission of which 

 will be to render the enemy's submarine mines harmless by cutting 

 their cables. This boat is also spindje- shaped, but only 15 feet 

 long by 5 feet 3 inches in diameter, and will have a crew of two- 

 men only, whereas the crew of the " Gymnote " is from six to eight 

 men. As the cubic capacity of this boat is comparatively small, 

 compressed oxygen is to be carried as part of the equipment. The 

 boat is to be provided with powerful scissors, working from inside, 

 by means of which it is intended to cut the electric cables of the 

 submarine mines. The screw is mounted on a swivel-shaft to fa- 



terior is afforded by a man-hole a little forward of the conning- 

 tower. The power for working this vessel is derived from a 

 battery of 564 Commelin & Demazures alkaline accumulators, 

 weighing, in working order, close upon 10 tons. A compound 

 switch is provided by means of which the battery can be differently 

 grouped ; the combinations being 12 cells parallel and 47 in series 

 for very slow speed, 6 in parallel and 94 in series for slow speed, 4 

 parallel and 141 in series for ordinary travelling speed, and 2 parallel 

 and 282 in series for fast speed. The weight of the battery per 

 horse-power is 83 pounds. The electric motor works the propeller 

 direct without the intervention of any speed-reducing gear, and has 

 been specially designed for this purpose by Capt. Krebs. It is a 

 sixteen-pole disk machine, weighing 2 tons, and developing 52 horse- 

 power at a speed of only 280 revolutions a minute. The armature 

 is 40 inches in diameter, and the winding is such as to require only 

 four brushes. The resistance of the machine is .16 of an ohm. 

 At full speed, the motor is sufficiently powerful to propel the boat 

 at a speed of 9 to 10 knots per hour ; the capacity of the battery 

 being said to correspond, under this condition, to about four and a 

 half hours of work, which would take the boat over a total dis- 

 tance of 40 to 45 knots. At a speed of 6 knots an hour, the total 



cilitate the manoeuvring, and is worked by an electric motor driven 

 by a battery of Schanscheiff primary cells. The boat is lighted by 

 five small glow-lamps ; and a small arc-lamp with a projector is 

 also provided, the beams of light from which can be thrown for- 

 ward through glass lenses fixed in the hull, so as to illuminate the 

 water for a certain distance ahead, and thus make the work possi- 

 ble for which this boat is especially intended. 



If this country is going to rely to a great extent on torpedoes as 

 a coast defence, the recent improvements in submarine boats can- 

 not but be of great interest to Americans. Congress recently 

 appropriated a considerable sum for the construction of such a ves- 

 sel, and, although nothing definite is known about the plans that 

 will be adopted, yet it is understood that electricity will not be the 

 motive power. 



NATURAL GAS IN OHIO IN 1888. 



A LATE number of the American Manufacturer has a careful 

 review of the natural-gas situation in Ohio, by Professor Edward 

 Orton, the State geologist, who says in effect that no important 

 discoveries have been made in Ohio during the year 1888, though a 



