670 KANSAS CITY REVIEW OF SCIENCE. 



rise in pressure^ but simply increased in volume, and following the piston as it 

 moves forward, the return stroke discharges the products of combustion. 



3. An engine in which a mixture of gas and air is compressed or introduced 

 under compression into a cylinder, or space at the end of a cylinder, and then 

 ignited while the volume remains constant and the pressure rises. Under this 

 pressure the piston moves forward, and the return stroke discharges the exhaust. 



Several minor types have been proposed and many modifications of these 

 three methods are used. A thorough understanding of these, however, renders 

 it possible to judge the merits of any other. 



Types I and 3 are explosion engines, the volume of the mixture remaining 

 constant while the pressure increases. Type 2 is a gradual combustion engine in 

 which the pressure is constant but the volume increases. 



The author, in the course of his experiments on gas engines, has found that 

 1,537° Centigrade is the temperature usually attained by the ignited gases in his 

 engine, and he has accordingly investigated the behaviour of air under different 

 conditions at this temperature. 



The results of his investigations are carefully and mathematically set forth in 

 this volume which will at least be interesting to engineers and physicists. 



The Use of Tobacco. J. I. D. Hinds, Ph.D., Lebanon, Tenn.; i2mo., pp. 

 138. 55c. by mail. 



Prof. Hinds is teacher of Chemistry in Cumberland University and has ac- 

 quired a high standing as a chemist as well as teacher of natural science, in the 

 South. His little work upon the Use of Tobacco gives evidence of his skill in 

 both departments, since it not only furnishes a chemical analysis of the plant, but 

 also gives its history, describes its botanical character and its physiological and 

 pathological effects upon the system. He makes the statement that nearly nine 

 hundred millions of the inhabitants of the globe are users of tobacco, and justly 

 claims that an article that holds subject nine-fourteenths of the human race is 

 certainly worthy of attention. 



The chapter upon its physiological effects is largely made up of quotations 

 from some of the best writers and thinkers of the day and is well worthy the care- 

 ful perusal of all persons addicted to the use of "the weed." It is a very inter- 

 esting and valuable monograph and should have a large distribution. 



The Brewer, Distiller and Wine Manufacturer. Edited by John Gard- 

 ner, F. C. S.; i2mo., pp. 278. Illustrated. P. Blakiston, Son & Co., Phil- 

 adelphia, 1883. $1.75. 



This is the first of a series of Technological Hand books designed to meet 

 the wants and pockets of those who need practical information on special subjects 

 and do not care to purchase cyclopaedias or expensive technological works. It 

 is intended to be equally valuable to the expert as to the beginner. This volume 



