486 THE POPULAR SCIENCE MONTHLY. 



in two complete strokes, but whether a fresh supply is taken or not is 

 determined by the governor, which acts to maintain a constant speed 

 under varying loads. It is of the ordinary ball form, and is placed in 

 the cup-shaped receptacle pendent from the cylinder. It actuates by 

 its movement a lever controlling the gas-valve, so that this is opened 

 and closed in accordance with changes in the speed. The regulation is 

 delicate, and the speed nearly if not quite as uniform as in a steam-en- 

 gine. The speed can be changed at will by increasing or diminishing 

 the amounts of air and gas which may be drawn in each time. An 

 automatic device is provided, which closes the gas-valve, should the 

 engine by any accident stop in a position in which this would be left 

 open. The oiling is committed almost entirely to the engine itself, the 

 only work i-equired in this connection being the filling of the oil-cups. 

 They are placed upon the top of the cylinder, and by means of the 

 small shaft and pulley driven from the lay-shaft deliver a given num- 

 ber of drops of oil to the slide-valve, cylinder, and piston at each revo- 

 lution. The exhaust is rendered noiseless by being passed into a cham- 

 ber, from which it escapes into the atmosphere under slight pressure. 

 The cylinder is water-jacketed to keep it cool, the circulation of the 

 water being maintained by the heat received, the warmer water rising 

 to the supply-tank and the cool taking its place. 



As before stated, the engine is very economical of gas. The amount 

 used per hour per indicated horse-power is stated by the makers to be 

 twenty-one and a half cubic feet, which, with gas at two dollars a 

 thousand, is a trifle above four cents. In first cost the engine is some- 

 what more expensive than a good steam-engine, including boiler, of 

 the same power, the price ranging from five hundred dollars for the 

 two horse to eight hundred and fifty for that of seven horse-power. 

 The former occupies a floor-space of about three feet by seven, and 

 weighs fourteen hundred pounds, and the latter covers somewhat more 

 space, and is of double the weight. 



The heat generated by the combustion of the gas has been very fully 

 utilized in this engine, but not to the greatest extent practicable. A 

 certain portion of it is carried off by the water in the jacket, and is 

 therefore wasted. If, instead of being allowed to escape without doing 

 any useful work, it was employed to convert a small quantity of water 

 injected into the cylinder into steam, overheating of the cylinder would 

 be prevented, and at the same time this heat would be utilized. Be- 

 sides the power gained, the use of steam is of value in giving a more 

 sustained pressure on the piston and in lubricating the cylinder. Nu- 

 merous attempts have been made to realize its advantages, both in 

 hot-air and gas engines, but in most cases with no considerable gain 

 in economy. The engine of Hugon, mentioned above, employed it, 

 but apparently with little advantage. 



Quite recently a gas-engine has been brought out in which the diflS- 

 culties seem to have been mostly overcome, and which appears to ap- 



