4 2 



always detect some fluctuation of brightness, which is often 

 aggravated by impurities and inequalities in the material of 

 the carbons. The diameter of these carbons is usually from 

 quarter inch to half inch, according to the power of the lamp ; 

 but there were one or two lamps in occasional use in the 

 Exhibition which had carbons of an inch or inch-and-half. In 

 a few of the systems, the carbons are placed parallel to each 

 other with some contrivance for making the current pass across 

 the ends and not anywhere else. In Jablochkoff 's system this 

 is secured by interposing kaolin or plaster of Paris, which 

 reaches not quite to the ends, and burns away just as fast as 

 the carbons ; but it was the universal verdict that of all the 

 lights in the Exhibition, the Jablochkoff were the most un- 

 steady. They are also said to be wasteful of power as compared 

 with other arc lights. 



But I must stop for the present my description of the objects 

 in the Exhibition, and proceed to speak of the Congress. It 

 was called the International Congress of Electricians, and was 

 held under the auspices of the French Government, the Min- 

 ister of Posts and Telegraphs being its President. 



Communications had been addressed to the Governments of 

 the various countries requesting each of them to appoint Com- 

 missioners whose business would be not only to select or make 

 provision for the selection of the members to be sent from their 

 own country to the Congress, but also to select their jurymen 

 and look after the interests of their country in the Exhibition 

 generally. 



The French members of the Congress had a preliminary 

 meeting, and drafted a programme which was substantially 

 adopted. There were to be two kinds of meetings, viz. : plenary 

 meetings, and sectional meetings, besides public lectures. 



The plenary meetings were for the discussion of questions 

 requiring an international agreement : and hence calling for a 

 vote of the Congress. 



The sectional meetings were for discussion and interchange 

 of ideas upon various electrical questions, which might, in some 

 instances, prepare the way for laying a resolution before *t 

 plenary meeting. 



