496 



NATURE 



[March 21, 1S95 



§ 2. A glass U-tube with vertical branches (Fig. I), each 

 18 inches long and about i-inch bore, with the upper 8 inches 

 of one of the branches carefully coated outside and inside with 

 clean shellac varnish, was held fixed by an uninsulated support 

 attached to the upper end of this branch. The other branch 

 was filled with little fragments of pumice soaked in strong 

 sulphuric acid or in water, and a fine platinum wire, wiih 

 one end touching the pumice, connected it to the insulated 

 electrode of a quadrant electrometer. A metal can, M, large 

 enough to surround both branches of the U-tube without 

 touching either, was placed so as to guard the tube from electric 

 infiuences of surrounding bodies, the most disturbing of which 

 is liable to be the woollen cloth sleeves of the experimenters or 

 observers moving in the neighbourhood. This metal can was 

 kept in metallic connection with the outside metal case of the 



calcium in lump:, not specially dried, gave no effect in the 

 straight tube ; but if previously heated to lSo° or 200° and put 

 into the straight tube when still hot, it gave an enormous positive 

 electrification immediately on the commencement of blowing. 

 Strong positive electrification was obtained a second time, by 

 discharging the electrometer to zero, re-insulating, and re- 

 commencing the blowing. But after discharging a second time, 

 re-insulating, and re commencing the blowing, no further elec- 

 trification was found. 



§ 4. In continuation of these experiments on September 25, 

 the arrangement represented in Fig. 2 was set up. The outer 

 metallic guard-vessel, M, was kept connected by a wire lo the 

 case, and to one pairof quadrants of a quadrant electrometer, E. 

 The water in the inner glass jar. A, was connected by a pla- 

 tinum wire to the oilier pair of quadrants of the electrometer. 



quadrant electrometer. The length of the exposed platinum 

 wire between the U-tube and the electrometer was so short that 

 it did not need a metal screen to guard it against irregular in- 

 fluences. An india rubber tube from an ordinary blow-pipe 

 bellows was connected to the uninsulated end of the U-tube. 

 Air was blown through it steadily for nearly an hour. With the 

 pumice soaked in strong sulphuric acid in the other branch, the 

 electrometer reading rose in the course of three-quarters of 

 an hour to about g volts positive. When (he pumice was moist- 

 tened :vit/t water, instead of sulphuric cuid, no such effect ivas 

 observed. The result of the first experiment proves decisively 

 that the passage of the air through the U-lube gave positive 

 electricity to the sulphuric acid, and therefore sent away the 

 dried air with negative electricity. A corresponding experi- 

 ment with fragment^ of pure chloride of calcium instead of 

 pumice in sulphuric acid, gave a similar result. In repetition 



Fig. 3. 



To have this inner jar well insulated, it was supported on a 

 block of parailin ; and the other end of the glass tube dipping 

 into the water was fitted into one end of a lube of paraffin, to 

 the other end of which was fitted a tube for ingress of air, from 

 bellows, as shown in the figure. The insulation of this arrange- 

 ment was found to be good. When air w.is blown through the 

 water it was found that the jar containing the water became 

 positively electrified. 



§ 5. To prevent splashing of water out of the jar, a paper 

 cover was put on its mouth, or the jar was tilted, as shown in 

 I" 'g- 3i so that the bubbles broke against the inside of the jar. 

 In three experiments thus made, the same electrification was 

 still found, amounting to about 6 volts positive in a quarter of 

 an hour. 



§ 6. As the jar was in every experiment positively electrified, 



J_ 



/ 



of the experiments, however, it was noticed that the strong 

 positive electrification of the U-tube seemed to commence some- 

 what suddenly when a gurgling sound — due lo the bubbling of 

 air through free liquid, whether sulphuric acid or chloride of 

 calcium solution in the bend of the U-tube — began lo be heard. 

 It ha^ iince been ascertained that it was because no linuid ac- 

 cumulated in the botlom of the U-tube that no electric effect 

 was found when the pumice was moivtened with pure water. 



% 3. .Arrangements were made to prevent any bubbling of the 

 .Vir through liquid, by using a straight lube insle.id of a U-tube. 

 In a large number of cxperimmts with pumice, moistened with 

 pure sulphuric acid in the straight lube, ond air blown through 

 for about half an hour, no definite electrification was obtained. 

 In this Mtaight lube, as formerly with (he U lube, pumice 

 moistened wilh pure water gave no electrification. Chloride ol 



NO. 1325, VOL. 51] 



Fin. ^. 



llie air, if unclcctrified ' when entering it, must have been 

 negatively electrified when leaving it. 



S 7. To lest if the air was negatively electrified after 

 bubbling, on October II the apparatus- shown in Fig. 4 was 

 set up. The apparatus consists of a large sheet iron vat, V v, 

 125 cm. in diameter and yocm. in height, iiwerled on a large 

 wooden tray lined with lead, anil supported by three blocks of 

 wood, liy filling the Iray with water llie air is confined in 

 the val. 



c ( is a mclal screen kept metallically connected with the 



I Air wan similarly blown from bellows into llie val (tee I 7)willioul snT 

 biilihlinK, anil no ekclrificition w.u observed. . 



-' The val, the wiilerdropi>er, and ihc elcclromclcr are Ihe same M in IM 

 apparalix. described in the I'lmecdingi of ihe Rojal Society, vol. 56, year 

 1894, " Klettrilicalion of Air," by Ixjrd Kelvin .ind Magnus Macle.-in. 



