472 



SCIENCE. 



[N. S. Vol. XI. No. 273. 



their behests to men through ghosts or dead 

 children by whistling sounds or whispered 

 words. Tattooing is permitted only when a 

 deity has given his assent by whistling ; house 

 spirits and the genii of trees give their revela- 

 tions by whispers only. A. S. G. 



APPLIED THEBiI0DYNA3IICS. 



In a recent publication of ' Documents sur la 

 Ldboratoire de Mecanique de V Univeraite de Liege,' 

 describing its methods of instruction, by the 

 Professor of Applied Mechanics and of Indus- 

 trial Physics, M. Dwelshauvers-Dery, we find 

 a resumi of researches in applied thermody- 

 namics, mainly in the experimental study of 

 the steam-engine, which is interesting as ex- 

 hibiting the character and extent of the work 

 recently performed, and valuable as supplying 

 important data previously unknown. 



This laboratory of applied mechanics was 

 completed in 1893, after, as the author of these 

 documents says, five years of constant solicita- 

 tion of the government to supply this 'auxiliaire 

 precieux,' of which M. Dwelshauvers-Dery was 

 the first to conceive the idea, a generation ago, 

 though so late in its realization. His idea vt-as 

 that of a laboratory of research and instruction 

 in engineering, to be employed in the work of 

 the regular courses leading to technical degrees 

 and devoted to the purposes of the student, 

 rather than, as previously usual in nearly all 

 departments of applied science, primarily for 

 those of the distinguished professor in charge 

 and only secondarily and incidentally for the 

 student. 



The researches which have been conducted 

 since the date of completion of this laboratory 

 by the Director, assisted by his staff and by 

 advanced and able students, have been mainly 

 in applied thermodynamics. M. Dwelshauvers- 

 Dery is a disciple of Hirn and aided in the 

 investigations made in Alsace at the beginning 

 of the work of his eminent leader. Since that 

 time, the famous discussion between Zeuner 

 and Hirn and their followers has made this 

 work and these workers familiar to all investi- 

 gators and students in that field. It has been 

 in the supplementing of Hirn's earlier work 

 that the experimental steam- ' plant ' at Li6ge 

 has been mainly occupied recently. 



Am^ong other investigations, those relating to 

 the influence of the water collecting in the 

 steam-chest of the engine upon its efficiency, 

 on the effect of superheating, on the use of the 

 steam-jacket, on the effect in the real engine of 

 compression, and those on the condition of the 

 vapor, as to ' quality,' in the clearance spaces, 

 have been the most extensive and important. 



It was found to be the unquestionable fact 

 that, with the engine employed, it was advan- 

 tageous to continually drain the water of con- 

 densation from the valve- chest of the engine 

 when using moist steam and whether the jacket 

 is in use or not. With superheated steam, 

 naturally, no effect was observed. 



The steam-jacket was found to give an 

 economy of from 24 to 28 per cent., either with 

 or without superheating ; the latter being a 

 disputed question until thus, for this case, at 

 least, settled. Superheating produced an 

 economy of about 20 per cent., as a maximum. 



The investigations of the quality of the 

 vapor in the compression period occupied 

 several years and attracted much attention and 

 some opposition to the conclusions reached was 

 manifested by a number of distinguished , ex- 

 perts in that department. Those experiments 

 which were made with ' constant absolute 

 work ' showed a decided loss by compression 

 and a loss proportional to the amount of the 

 compression ; which fact was attributed to the 

 heat-exchanges between vapor and cylinder- 

 wall. This conclusion was challenged and it 

 was denied that the fundamental assumption 

 that, as asserted by Hirn, the steam at the end 

 of emission is dry, could be accepted as true. 

 Dwelshauvers-Dery and his former assistant 

 and pupil, Duchesne, furnished proof of the 

 correctness of his proposition. (Revue de 

 Mecanique, Jan., 1899 ; July, 1899.) 



Mr. Isherwood, the famous pioneer in this 

 class of work and the Engineer-in-chief of the 

 navy during our civil war, suggested that the 

 experiments be repeated, making the ' indi- 

 cated work ' a constant quantity. He thought 

 it possible that it might be found that the use 

 of compression was neither economical nor 

 wasteful in the actual case and, therefore, its 

 use simply a question of smoothness of oper- 

 ation of the machine and entirely outside 



