OF ARTS AND SCIENCES. 37 



Investigations on Light and Heat, made and pcBLisnED whollt or in pakt wrra 

 Appropriation from the Rumford Fund. 



III. 



ON A THERMO-ELECTRIC METHOD OF STUDYING 

 CYLINDER CONDENSATION IN STEAM- 

 ENGINES.* 



By Edwin H. Hall. 



Presented January 11, 1893. 



Before the time of James Watt the steam in an engine cylinder 

 was condensed, and so gotten rid of, after it had done its work, by 

 pouring cold water directly upon or into the cylinder. So, when- 

 ever steam was admitted for a new stroke, a great part of it was 

 condensed in the act of reheating the cylinder wall; whence the 

 term cylinder condensation. Watt invented and brought into use 

 the independent condenser, by means of which the steam is re- 

 moved from the cylinder with comparatively little cooling of the 

 latter. It is believed, however, that even now cylinder condensa- 

 tion wastes a good deal of steam in common engines, whether con- 

 densing or non-condensing. The commonly accepted theory is, that 

 during the exhaust the wall of the cylinder, to a certain depth from 

 the steam space, or a layer of water upon the cylinder wall, be- 

 comes cooled by the evaporation which accompanies exhaustion, 

 and that the incoming steam finds this wall, or the laj'er of water 

 upon it, considerably cooler than itself. It is believed that some 

 part of the steam which is thus condensed upon the cylinder wall 

 during admission is recovered during the later part of i\\e forward 

 stroke by re-evaporation, but that a considerable amount, sometimes 



* An informal account of much that is contained in this article was given 

 before the Academy in May, 1891. A similar account was given before the 

 American Institute of Electrical P^ngineers in New York, May 20, 1891, and was 

 printed in the Transactions of tliat Society. 



