154 



SCIENCE. 



[N. S. Vol. V. No. 108. 



wastes a large part of the heat which it trans- 

 mits to the working charge ; transmitting it 

 through the cylinder-wall too late in the stroke 

 to be of much service, or even so late as to be 

 absolutely lost by passage into the cylinder 

 during the period of exhaust, instead of, as 

 necessary for best results, early in the induction 

 period. Both in using the steam-jacket and in 

 superheating, the reduction of the waste by 

 initial condensation fails to give commensurate 

 gain in work performed by the unit weight of 

 steami. In one instance, for example, a reduc- 

 tion of initial condensation by ten per cent, 

 only gave increase of work to the extent of two 

 and a-half per cent. In another instance a 

 reduction of wastes by twelve per cent, gave a 

 gain of work of only three per cent. The action 

 of superheated steam is more favorable, and 

 the gain in work done and increased eihciency 

 amounts to more nearly one-half the percentage 

 of reduction of wastes by initial condensation. 



The steam was condensed in a surface-con- 

 denser. The mean quantity of steam condensed 

 per hour and per square meter was 13 kgs. 

 The mean quantity of heat abstracted per kg. 

 of steam was 567. 7 calories. The mean quantity 

 of heat traversing the condensing surfaces was 

 7,402 calories per hour and per square meter. 

 The cylinder-heads transmitted nearly twice 

 this quantity from their jackets into the cylin- 

 der, and the cylindrical jacket of the cylinder 

 proper about one -fifth as much as the trans- 

 mission into the condenser. 



'Cylinder condensation,' during the brief 

 period of its action on this engine, occurred at 

 the enormous rate of 494,600 calories per hour 

 hour and per square meter — seventy times as 

 rapidly as in the surface condenser — and illus- 

 trates the most rapid transfer of heat known to 

 the engineer or the man of science. Mon. 

 Dwelshauvers is probably the first to measure 

 this figure with any degree of accuracy, though 

 Cotteril, long ago, gave us the general facts 

 and approximate computations. 



A very important and, to the experimenter, 

 an unexpected, development was, as stated by 

 him, the following: "With steam superheated 

 to 166° C. at its entrance into the engine, and 

 with saturated steam at 155° C. stagnant in the 

 jackets, the use of the jacket gave an economy 



of 20 per cent, and over by reducing the initial 

 condensation."* 



The fact is now incontestable and it is easily 

 seen that, so long as the action of the su- 

 perheated steam is not such as to completely 

 extinguish initial condensation by bringing the 

 temperature of the cylinder wall fully up to 

 that of the saturated boiler steam, the jacket may 

 still find opportunity to reinforce the action of 

 the superheated steam by doing some work in 

 the interval between the instant of closing of 

 the induction valve and that of its reopening in 

 the succeeding cycle. 



These contributions to our knowledge of the 

 interior workings of heat and steam in the en- 

 gine will undoubtedly be received as among 

 the most important yet placed on record in the 

 history of the experimental investigation of 

 the steam-engine, and M. Dwelshauvers-Dery, 

 through these researches, as an earnest and 

 worthy disciple and successor to Hirn, will earn 

 an enviable distinction. R. H. Thurston. 



COENELL TJNIVEESITY. 



Prehistoric Man and Beast. By Rev. H. N. 



Hutchinson, B. A., etc. Illustrated. D. 



Appleton & Co. 1897. pp. 298. 



Mr. Hutchinson, already known to the read- 

 ers of general literature by his works, ' Ex- 

 tinct Monsters,' etc., has endeavored, in the 

 present volume, to present, in equally popular 

 style, some of the latest results of geology and 

 archaeology with regard to primitive man. 



He distinctly disclaims writing for special 

 students in either of these branches, and also 

 oflers himself solely as an interpreter of the 

 opinions of others, and 'not as a Brahmin.' 

 Nevertheless, he espouses very warmly, and 

 claims as quite decided, various opinions which 

 the ' specialist, ' if he is fair-minded, considers 

 still undetermined. For example, he heads one 

 chapter ' The Myth of the Great Ice Sheet, ' and 

 assumes as incontrovertible Sir Henry Ho- 

 worth's contention that the ice sheet of glacial 



*This fact was asserted by the writer some years 

 ago and was challenged by various authorities, 

 including M. Dwelshauvers, who has since given us 

 these facts and has frankly reversed his position. 

 \ide Manual of the Steam Engine ( R. H. T. ), Vol. I. ; 

 Sees. 145, 153, pp. 598, 697; and Trans. A. S. M. E., 

 Nov., 1889 ; Journal Franklin Inst., Dec., 1889. 



