118 ANNUAL OF SCIENTIFIC DISCOVERY. 



ment was tried. Near a large belt in the carding-room was a gas- 

 burner, and on a bench between them there was placed a small quan- 

 tity of wool, which is a non-conductor of electricity. If a person 

 stood upon this wool, reaching one hand within two or three inches of 

 the belt, and touching the gas-burner with one finger of the other, the 

 escaping gas was at once ignited with an explosion like that of a per- 

 cussion cap, the body of the operator thus being made the medium 

 for conducting the electricity. 



The writer adds," We shall be able to make a great saving of 

 expense in the woollen manufacture as soon as we can discover an 

 effective method of conducting the electricity away from the cards, as 

 we shall then be able to dispense entirely with the use of oil on the 

 wool, which will save at least $30,000 per annum, when the mills 

 are in full operation." Editors. 



ON THE PRODUCTION OF LIGHTNING BY RAIN. 



WE find, in Brewster's Magazine for Sept., a paper communicated by 

 W. R. Birt, on the production of lightning by rain. The authors atten- 

 tion was attracted to this subject by a question put in the report of the 

 Committee on Physics of the Royal Society, who say, " There is one 

 point to which we wish that some attention might be paid : it is the 

 sudden gush of rain which is almost sure to succeed a violent detonation 

 immediately overhead. Is this rain a cause or consequence of the electric 

 discharge 1 We are not aware that the former view has ever been 

 maintained or even suggested. Yet it is very defensible. In the sudden 



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agglomeration of many minute and feebly electrified globules into one 

 rain-drop, the quantity of the electricity is increased in a greater propor- 

 tion than the surface over which (according to the laws of electric distri- 

 bution) it is spread. Its tension, therefore, is increased, and may attain 

 the point when it is capable of separating from the drop to seek the sur- 

 face of the cloud, or of the newly formed descending body of rain, 

 which, under such circumstances, and with respect to electricity of 

 such a tension, may be regarded as a conducting medium. Arrived 

 at this surface, the tension, for the same reason, becomes enormous, 

 and a flash escapes." As we have said, Mr. Birt was induced by 

 this paragraph to commence some observations on the fall of rain 

 during thunderstorms, and his first opportunity was on July 25th, 

 when, during a thunderstorm, a sudden gush of heavy rain occurred, 

 which, within two seconds, was succeeded by a vivid flash of light- 

 ning, and the thunder of course followed this. On the 26th, he had 

 several opportunities of noticing, as there were a number of showers 

 during the day, and on every occasion he is quite certain that the 

 sudden gush of rain preceded the electric discharge. The storm of the 

 26th was a very severe one, and several houses were struck in the 

 immediate vicinity of the writer's residence at Bethnal Green. He is 

 of the opinion that, as is suggested in the passage quoted above, an 

 agglomeration of the smaller drops took place, increasing the electric 

 tension to such an enormous extent, that a flash escaped in the imme- 

 diate neighbourhood of the houses struck, and thus entered them. 



