KAIN AND ITS ORIGIN IN THUNDERSTORMS. 395 



In 1892 Professor LENARD* published his well-known work on the electrification 

 of water by splashing, and in that work he had made experiments on the question 

 here raised, but had come to the following conclusion, which he printed in italics : 

 " Thus mere breaking up of the water is just as ineffective as the falling of streams 

 of water through the air ; it was only the impact of separate drops upon a flat 

 obstacle which produced an electrical effect, "t 



The experiments on which this conclusion was based did not appear conclusive, 

 and it was considered necessary to make further experiments before accepting it as 

 final. 



The first experiments made led to negative results, but it was soon found that 

 this was probably due to the impurity of the water drawn from the Simla mains, for 

 even the Lenard effect could not be obtained with it. The experiments were then 

 repeated with distilled water, and it was at once found that the mere breaking up 

 of large drops into spray on an air jet gave to the water a considerable positive 

 charge. 



There is no need to describe in detail the experiments by which this result was 

 first obtained, for better methods, capable of giving quantitative results, were 

 developed later, and a description of the final experiments will at once be given. 



A metal tray T (see fig. 2), 30 cm. square and 15 cm. deep, was supported on three 

 amber insulators I, while through the bottom of the tray, exactly in the middle, 

 a vertical piece of glass tube was passed which was drawn out to a nozzle 2 nun. in 

 diameter at its upper end. Underneath the tray this glass tube was connected by 

 means of a short piece of rubber tube to another glass tube S, which had been coated 

 inside and out with sulphur. The latter formed a very highly insulating txibe, by 

 means of which the nozzle in the tray could be connected to the air reservoir R and 

 air passed through it without any fear of the charge collected on the tray being 

 conducted away. The reservoir was supplied with air by means of the foot bellows 

 B, and the pressure inside could be kept fairly constant by observing the water 

 manometer M. 



At a distance of about 70 cm. above the nozzle a glass funnel F was fixed, 

 connected to a glass tube ending within a metal cylinder C. The glass tube was 

 filled with wires by which the flow of water out of the funnel could be regulated 

 until large drops fell from the end of the tube at the rate of about 80 a minute. 

 The cylinder C was insulated from the funnel, and could be either connected to earth 

 or to batteries, according as to whether it was desired to have the falling drops 

 electrically neutral or charged. 



By adjusting the position of the funnel it could be arranged that each drop fell 



* ' Wied. Annal.,' vol. 46, pp. 584-636, 1892. 



t Blosses Zerstieben des Wassers ist also ebenso unwirksam wie das Hindurchfahren von Strahlen 

 durch die Luft; nur Auftreffen getrennter Tropfen auf ein flaches Hinderniss gab stets electrische 

 Wirkung. 



3 E 2 



