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LORD KELVIN, DR. M. MACLEAN, AND MR. A. GALT, ON THE 



26. The greatest effect, 4'5 volts negative, was obtained, as was to be expected 

 from LENARD'S discovery, when the air was withdrawn from a point well down in the 

 can, the can being close to the funnel, and the falling water rattling on the bottom of 

 the can. Decreasing effects were observed (l) when the air was withdrawn from the 

 can at increasing distances from the bottom ; (2) when several inches of water were 

 kept in the can ;* (3) when air was drawn from the funnel, and the distance between 

 the can and the funnel was gradually increased. 



27. A filter of 100 wire gauzes gave at the rate of 26 volts, and a filter of 

 2 gauzes, with a loose plug of cotton wool between them, gave 6 '3 volts, in the same 

 time and under the same conditions as the filter of 50 wire gauzes gave ( 26) 4'5 volts, 



28. A sloping metallic plate was next fitted to the bottom of the funnel in such a 

 way that the falling water on striking the plate passed out by the aperture between 

 the funnel and the lower edge of the plate. In each experiment 120 strokes of the 

 pump were taken at the rate of 40 strokes per minute. Drawing the air from the 

 aperture near the bottom of the funnel gave, in 4 experiments, results averaging about 

 8 volts. These results were given by a filter containing 2 brass gauzes with cotton 

 wool between them. 



29. Two simple brass tubes of different bores with no wire gauze or cotton wool 

 were now tried as filters. Each was 10 ceutims. long and 1 centim. external 

 diameter. The following results were obtained : 



Using the brass filter of 0'18 centim. bore, drawing from the aperture near the 

 bottom, and varying the water pressure, we found mean results as follows : 



Full pressure . . . . . '. ."....,. . 3*4 volts. 



Diminished pressure 2'6 ,, 



.Very low pressure (200 drops per minute) . . 0'17 



30. In the long metallic tube between the funnel and the testing filter we placed, 

 in successive experiments, an increasing number of brass gauzes and plugs of wool. 



* See a Paper by LENARD on ' Electricity of Waterfalls," ' Wied. Ann.,' 1892, vol. 4fi, pp. 584-636. 



