454 



A. E. Kennelly — Alternating Currents. 



for the purpose of investigating this matter show that under 

 certain conditions the quantity of gas liberated is in very close 

 accordance with that which a continuous current of equal 

 strength would supply, and hence afford ground for the hope 

 that it will shortly be possible to measure the strengths of 

 alternating currents by the voltameter as closely and as con- 

 veniently as in the case of continuous currents. 



Two methods have been tried. (1) The condenser method , 

 or incomplete metallic circuit. (2) The ordinary method with 

 complete metallic-and-liquid circuit. 



Several series of measurements have been made, all agreeing 

 very fairly. The following series taken at one time will suffice 

 for all. 



The source of the alternating current was a Siemen's alter- 

 nating dynamo machine designed for 100 volts, the electro- 

 motive force being readily under control through the current 

 in its field magnets ; the speed of revolution on the occa- 

 sion of this experiment was steady at 1470 per minute. At 

 this speed its alternations, being 8 to the revolution, are 196 

 per second. 



The voltameter was of special construction. An ordinary 

 glass evaporating dish ll*5 cms in diameter and 6*3 high was 

 filled about two-thirds with a 10 per cent (by weight) solution 

 of pure sulphuric acid in distilled water, the density of this 

 •solution being 1*065 at 19° C. At the bottom of the dish was 

 immersed a disk of resinous material 5 cms in diameter and l # 2 cm8 

 high. Twelve platinum wires of different lengths but equal 





















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diameter (0'01T8 cms ) projected vertically from the upper surface 

 of the disk, so as to stand in a ring of 4 cms diameter and equi- 

 distant from each other. These wires were ranged from 1 -5 cm8 

 down to # 025 cms in length, the corresponding wires across one 

 diameter having' as closely as possible equal lengths. Connec- 

 tions with rubber-covered wires sealed in the material of the 



