RURAL ENGINEERING. 485 



"(3) For automobile air-cooled engines alcohol seems to be especially adapted 

 as a fuel, since tlie temperature of the engine cylinder may rise much higher 

 before auto-ignition takes place than is possible with gasoline fuel ; and if auto- 

 iguitiou of the alcohol fuel does occur no injurious hammeriug can result. 



"(4) The consumption of fuel in pounds per brake horsepower, whether the 

 fuel is gasoline or alcohol, depends chietly upon the horsepower at which the 

 engine is being run and upon the setting of the fuel supply valve. It is easily 

 possible for the fuel consumption per horsepower hour to be increased to double 

 the best value, either by running the engine on a load below its full power or 

 by a poor setting of the fuel supplj' valve. 



"(5) These investigations also showed that the fuel consumption was affected 

 by the time of iguitiou, by the speed, and by the initial compression of the fuel 

 charge. No tests were made to determine the maximum possible change in fuel 

 consumption that could be produced by changing the time of ignition, but when 

 near the best fuel consumption it was shown to be important to have an early 

 ignition. So far as tegted the alcohol fuel consumption was better at low than 

 at high speeds. So far as investigated, increasing the initial compression from 

 70 to 125 lbs. produced only i very slight improvement in the consumption of 

 alcohol. 



"(0) it is probable that for any given engine the fuel consumption is also 

 affecttd by the qv.autity and temperature of cooling water used and the nature 

 of the cooling system, by the type of ignition apparatus, by the quantity and 

 qviality of lubricating oil, by the temperature and humidity of the atmosphere, 

 and by the initial temperature of the fuel. 



"(7) It seems probable that all well-constructed engines of the same size will 

 have approximately the same fuel consumption when working under the most 

 advantageous conditions. 



"(8) With any good small stationary engine as small a fuel consumption as 

 0.70 lb. of gasoline, or 1.16 lb. of alcohol per brake horsepower hour may reason- 

 ably be expected under favorable conditions. These values correspond to 0.118 

 and 0.170 gal. respectively, or 0.95 pint of gasoline and 1.36 pints of alcohol. 

 Based on the high calorific values of 21,120 British thermal units per pound of 

 gasoline and 11,880 per pound of alcohol, these consumptions represent thermal 

 efficiencies of 17.2 per cent for gasoline and 18.5 per cent for alcohol. 



"But calculated on the basis of the low calorific values of 19,660 British 

 thermal unifs per pound for gasoline and 10,620 for alcohol, the thermal effi- 

 ciencies become 18.5 for the former fuel and 20.7 for alcohol. The ratio of the 

 high calorific values used above is, gasoline to alcohol, 1.78. The corresponding 

 ratio of the low calorific values is 1.85. The ratio of the consumptions men- 

 tioned above is, alcohol to gasoline, 1.66 by weight, or 1.44 by volume." 



Comparative values of alcohol and gasoline for light and power, J. B. 

 Davidson and M. L. King (loica Sta. Bui. 93, pp. 2.'i. flgs. 1.2). — The investi- 

 gations of which those here reported form a part were undertaken '* for the 

 purpose of making a comparison between (1) the heat value of the fuels, 

 (2) their economy in the production of light, (3) their economy in the produc- 

 tion of power, and (4) the relative safety of alcohol and gasoline for gen- 

 eral use." 



Studies of illuminating power were made with 3 forms of gravity lamps, a 

 wick gasoline lamp, a pressure over-head generator lamp, and an ordinary 

 kerosene lamp. The tests of power production were made with 3 ditferent 

 makes of gasoline engines having ordinary compression pressures. It was 

 found impossible to secure an engine especially designed for alcohol, "and it 

 was further found practically impossible to properly alter the design of any of 



