150 Messrs. Maclean and Makita Goto on the 



an hour. To make it sure we made more than 15 observa- 

 tions under different conditions, but always with the same 

 result, and we came to the conclusion that the water rushing 

 through the air electrifies it negatively, at least it does 

 so electrify common air full of dust. This result is in 

 accordance with the well-known change of atmospheric 

 electricity to negative during rainy weather. 



The following are the results which prove our conclusion : — 



(1) After negatively electrifying the air inside the vat by 

 making water drop through it for some time, if it is replaced 

 by the air outside of the vat, the electrometer-reading comes 

 down towards zero. 



(2) Simultaneous observations of the electrification of the 

 air inside the vat by the same means and of the air in the 

 room were made. After about 13 minutes the former ex- 

 ceeded the latter, though at that time the air of the room was 

 being electrified negatively by the paraffin lamp used in 

 reading the scale. 



(3) After starting the water-dropper and taking the elec- 

 trometer-readings for some time, say 10 minutes, if it is stopped 

 say for 10 minutes and again started, the initial reading is 

 the same as that just before the interval of stopping, and 

 it again continues to go up. 



(4) Whether the water-dropper was insulated or connected 

 to water-pipe by a wire, by connecting it to the electrometer 

 for taking the reading it shows that the negative electrifica- 

 tion of the air inside the vat goes on increasing for about half 

 an hour. 



(5) No difference in the result was found after painting 

 the inside of the vat. Before painting it presented the sur- 

 face of rusted iron. 



(6) Whether the vat is filled with air electrified positively 

 or negatively before the observation, the electrometer-reading 

 equally goes towards the negative side. 



(7) The maximum potential obtained was 5J volts negative, 

 but the more the air became free of dust the less became the 

 maximum reached. This is shown by the curves in fig. 2. 

 The curve No. 1 was obtained by observation after filling the 

 vat with the air of the room. The curve No. 5 was obtained 

 after continuous running of the aspirator for about 25 hours. 

 Intermediate curves correspond to the intermediate state of 

 the air as to its purity. In the curve No. 2 the water- 

 dropper was running for some time before beginning the 

 observation. 



(8) After putting water into the water-dropper and wait- 



