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On a Modification of Maxwell's Electrical Theory. 175 



burner " with a light-giving power of 33 candles, 

 on the other side a standard candle. As the candle 

 was gradually brought nearer the rotating photo- 

 meter, the illumination and hues of the portions a 

 and b (fig. 17) of the photometric ring approached 

 equality, and when the candle was at a certain 

 distance the difference of illumination and hues 

 of a and b become indistinguishable, and only a 

 band with a breadth of a-\-b with a uniform 

 surface was observed on the sides of the photo- 

 metric ring. 



The measures of the intensity of the light of the 

 Welsbach lamp in terms of the standard candle 

 were made by a friend. He made sixteen measures 

 with my Rotating- disk Photometer and sixteen 

 with the Bunsen Photometer. 



The mean of the series of measures made with 

 the Rotating-disk Photometer differed from the 

 mean of the departure of the maximum and mini- 

 mum measures from the mean by 1*49 per cent, 

 of the mean intensity of the light of the Welsbach 

 lamp. 



The mean of the series of measures made with 

 the Bunsen Photometer differed from the mean of Fig,!8. 

 the departure of the maximum and minimum 

 measures from the mean by 5*22 per cent, of the mean 

 intensity of the light of the Welsbach lamp. 



Hoboken, N. J., U.S.A., 

 April 15, 1893. 



XVI. Notes on a Modification of Maxwell's Electrical Theory. 

 By Alex. M c Aulay, M.A., University of Tasmania *. 



1. TN the Phil. Trans., 1892, p. 685, I have developed a 

 J- modification of Maxwell's electrical theory. As frequent 

 mention of this paper will be made below, it will be referred 

 to briefly as ' Electromag.' The principal object of the 

 paper was to free Maxwell's theory from certain difficulties I 

 felt in applying it to gross matter, but I was careful to point 

 out at the beginning that the theory developed might require 

 serious modification for the sether. The principal object of 

 the present paper is briefly to consider what modifications, if 

 any, are required. 



2. We shall require a proposition analogous to Prop. I. 



* Communicated by the Author. 



