On the Conductivity of the Hot Gases from Flames. 29 



effect on the value obtained for J. An error in the standard 

 of electromotive force of about ,' () per cent, would therefore 

 suffice to account for the entire difference between Rowland's 

 results and Griffiths'. 



The most interesting result of the present comparisons is 

 that Rowland's corrected curve shows the same rate of change 

 in the specific heat of water with the temperature between 

 15° and 25° that Griffiths' does, as can be seen at a glance by 

 an inspection of the curves as drawn in fig. 4. This fact also 

 suggests the possibility of the difference being due to an 

 error in the standards used, rather than in the experiments 

 themselves. 



A short abstract of the results of these comparisons was 

 published in the Johns Hopkins University Circular for June 

 1897, giving the corrected values of the mechanical equi- 

 valent of heat. There was a slight error in the values as 

 published, owing to the use of an incorrect method of reducing 

 the readings of Rowland's Baudin thermometers. The error 

 was not discovered until after the abstract had been published. 

 This incorrect abstract was reproduced in the Philosophical 

 Magazine for August 1897. 



The author wishes to express his appreciation of Professor 

 Rowland's kindness in allowing the use of his thermometers 

 for these comparisons, and his obligation to Professor Rowland 

 and Professor Ames for their frequent aid and advice in the 

 course of the work. 



Although the general plan of the apparatus described here 

 is the author's, he wishes to express his deep sense of obliga- 

 tion to Dr. W. T. Mather, at that time Fellow of Johns 

 Hopkins University, for his aid at almost every step in the 

 mechanical details of its design and construction. 



II. On the Conductivity of the Hot Gases from Flames. 

 By J. A. McClelland, M.A., Cavendish Laboratory, 

 Cambridge*. 



IT is well known that a charged body loses its charge when 

 a flame is brought near it, even if there is not actual 

 contact with the flame but only with the hot gases coming 

 from it. 



The subject of the conductivity of flames has been studied 



by many experimenters, and an account of their results is 



given in Wiedemann's Lehre von der Elecktricitdt, vol. 4 B, 



and in a later paper by Arrhenius (Wied. Ann. xlii. 1891). 



In the following paper the nature of the conductivity not 



* Communicated by Prof. J. J. Thomson. 



