MECHANICS AND USEFUL ARTS. 89 



action of diluted sulphuric acid on iron or zinc. It consists of 3 

 large earthenware bottles. It has been used, and may be used 

 again if occasion require it. Two men were at work in the gas 

 department. 



" The whole quantity of gas burned in the 12 hours upon the 6 

 jets is about 560 cubic feet, which is nearly at the rate of 7 7-10 

 cubic feet per jet per hour. The proportion of the 2 gases is about 

 248 oxygen to 312 hydrogen, or 1 to 1.26 ; if the gases were pure 

 it should be as 1 to 2. The introduction of the common air at 

 the charging will account for much of this, impurity of the man- 

 ganese for much more." Social Science Review. 



THE SPAKOWSKI NIGHT SIGNAL. 



In Commander Colomb and Captain Bolton's systems of flash- 

 ing signals, the longer or shorter flashes correspond to the dots 



and dashes (- ) of the Morse telegraph code, now well 



known. A new signal light, Spakowskfs, just introduced for 

 trial into the navy, promises to give great extension to this system 

 of signalling. It enables the light to be readily seen, even in hazy 

 nights, and without night-glasses, at a distance of 7 miles. The 

 instrument weighs 7 pounds, and is about 3 feet in length. The 

 staff, of about 2 inches diameter, is a hollow cylinder, inside of 

 which is fitted a piston that can be pressed down to two separate 

 distances in the cylinder, but which, when not in use, is kept in 

 the upper portion of the cylinder by a strong spiral spring in the 

 lower part of the cylinder or staff. Immediately over the top of 

 the piston, and at the upper part of the c}'linder, is a projecting 

 nozzle-pipe, through which the air finds entrance on the opening 

 of a valve, by drawing the piston downward. The upper portion 

 of the cylinder is now full of air, which will be driven out on the 

 piston being released by the operator's hand, and left to the up- 

 ward pressure of the spiral spring underneath. Let us look at the 

 upper portion of the instrument first. Here a cotton wick is burn- 

 ing from a small spirit-of-wine lamp fixed in the head of the instru- 

 ment. Opposite to the flame of the lamp is about an inch of hori- 

 zontally fixed brass tubing, of about the thickness of whip-cord, 

 terminating in a needle-point from another piece of the same 

 tubing, the one being the continuation of the other, and pointing 

 direct at the spirit flame. A reservoir in the head of the instru- 

 ment contains a little over half a pint of petroleum, and this res- 

 ervoir is connected with the two small pieces of tubing, and by 

 means of them subsequently with the 'air from the cylinder belo\v. 

 Now the piston being released, it is driven upward by the spring 

 underneath, and forces the air through the small tubes in the face 

 of the flame, and with it the petroleum in the form of vapor. The 

 result of this is a column of flame of full 2i inches in diameter, 

 which darts upward from the point of contact between the petro- 

 leum vapor and the flame of the lamp, and this column of light 

 lasts just so long as the piston is moving upward again to its nor- 

 mal position in" the cylinder. The length of time during which 

 the column of light is shown, therefore, depends upon the length 



8* 



