212 Kansas Academy of Science. 



pressure in such a manner that it is sprayed on entering, and the 

 high temperature produced in the air by the compression is suffi- 

 cient to ignite it. Its cycle is the nearest approach to the ideal 

 cycle first demonstrated by Carnot, the distinguished French sci- 

 entist and engineer, that has ever .been secured in engineering 

 practice. The engine is very efficient and is meeting with a good 

 demand, mostly for use in electric-generating plants, which is the 

 most exacting service to be met. So long as the petroleum supply 

 remains abundant it must be considered as an important prime 

 mover, and in this respect is far superior to the gas-engine using 

 natural gas. Since the fuels used in the two remaining types of 

 internal-combustion engines, namely, gasoline and kerosene, are 

 products of petroleum and comparatively expensive, those forms 

 are not to be considered, excepting at isolated points where small 

 powers are needed. 



As machines these two internal-combustion engines which we 

 may consider seriously in the present connection, namely, the gas- 

 and oil-engines, are compact and well constructed, occupying small 

 space in proportion to the power. All are probably familiar with 

 small types of the gas-engine, and it may be that many have in 

 their minds the idea of a small, noisy, and, perhaps, "cranky" 

 affair, which features are sometimes characteristic of the type. An 

 inspection of a large modern engine would do much to dispel that 

 idea. The small engine usually works with but one effective im- 

 pulse from the combustion or explosion of the gas in two complete 

 revolutions, according to the so-called Otto or four-stroke cycle. 

 This necessitates a very heavy balance-wheel, and increases the 

 difficulties of governing the speed, but it is very generally accepted 

 as the best method of securing efficient utilization of the heat 

 energy of the gas. When large powers are necessary, two or more 

 engines are usually connected to the same shaft, and set so that 

 their impulses alternate, thus securing more uniform expenditure 

 of energy, and making possible extremely accurate governing of 

 the speed. Both vertical and horizontal types are successfully em- 

 ployed. 



The latest designs of large power engines by the Westinghouse 

 Machine Company are strikingly similar in general appearance to 

 some makes of tandem compound high-speed steam-engines, ex- 

 cepting for the nature of the valve gear. They have two cylinders 

 in line, with pistons on the same rod, and both cylinders double 

 acting. Hence, instead of having but one impulse in two revolu- 

 tions or four strokes, each cylinder gives one impulse every two 



