183 



April 16, 1849. 



J. B. YATES, Esq., in the Chair. 



Mr. W. M. Eishee was elected a Member of the Society. 



Mr. Waldie made some remarks upon the expansion of 

 steam. He had some time previously brought before the 

 notice of the Society, the alleged discovery of an American 

 gentleman, that steam, when separated from water, did not 

 follow the ordinary laws of expansion by heat, that air or other 

 gases did. Mr. W. had from the first suspected that there 

 must be some fallacy in the experiments from which the fact 

 had been deduced, but had been unable to demonstrate it 

 satisfactorily till a few days ago. The observations were origi- 

 nally made in a syphon tube, the short end of which was 

 closed, and used as a receptacle for the steam to be experi- 

 mented on, which was confined by mercury. The source of 

 the fallacy was, that in cooling from a temperature higher than 

 212° the vapour condensed in the form of a dew on the sides 

 of the glass tube, and was retained there all along the inside 

 of the short leg of the syphon by the mercury rising to fill the 

 tube when the temperature was reduced below 212°. On 

 heating to 212° to obtain an unit volume of steam, this occu- 

 pied only a portion of the short end of the syphon ; but when 

 this was heated and expanded, it received a new supply of 

 water from the sides of the tube to be converted into vapour. 

 Mr. Waldie had prepared an apparatus by which this source 

 of fallacy was avoided, and had found, by experiment, that 

 there was no reason to suppose that steam did not expand by 

 heat in the same ratio as other gases. 



