ATMOSPHERIC ELECTRICITY. 307 



of varnished wire, or an electrometer, according to the object. The 

 electricity which descends along this wire being always of the same 

 nature with that of the cloud, we ascertain the cliaracter of the one 

 by observing that of the other. It was with a similar apparatus, well 

 insulated and protected as far as possible from the ch'anical action 

 of moisture, that M. Peltier made numerous and important observa- 

 tions on the electrical phenomena which take place during storms. 

 We might accomplish the same object by the use of the kite, as 

 many observers have done ; but, as we have seen, the danger of this 

 movable apparatus in stormy weather is so great that prudence alone 

 ought to forbid its use in this case. Besides, the facts which it fur- 

 nishes can be obtained, as it appears to me, equallj^ well by the use of 

 stationary apparatus. For in the great number of cases, not to say 

 all, the kite can only be influenced by the lower clouds ; we can 

 ascertain nothing respecting the ranges lying above these clouds, or 

 discover what belongs to each one of them, and thus furnish the 

 means necessary to an analysis of the different phenomena which 

 concur in the formation of storms. We believe that an insulated wire, 

 arranged like that which M. Peltier used, and affording all possible 

 security, will accomplish the same object much more conveniently. 



But if the use of the kite possesses little advantage in stormy 

 weather, it is not so when we use it in clear weather. It may then 

 render eminent service to science, and it was by means of it that 

 De Romas, Beccaria, Cavallo, and many other observers ascertained 

 the fact that the influence of atmospheric electricity increases in pro- 

 portion to the distance from the surface of the earth. It furnishes 

 a simple means of determining the law according to which this in- 

 crease takes place, a law which is not yet known, but which evidently 

 depends on the want of conductibility of the constituent parts of the 

 air, and must consequently vary on account of the vapor which rises 

 from the ground, or which settles on the earth. M. Peltier* has suc- 

 cessfully used the kite to accomplish this object. He ascertained 

 the height to which it ascended by employing an insulated drum, 

 around which the metallic wire was coiled, and furnished with an 

 index which constantly showed the length of wire given out. If we 

 would ascertain the height, let the cord be the hypothenuse of a 

 right-angled triangle, of which one of the sides is the perpendicular 

 height of the kite. If we wish to examine atmospheric electricty 

 at very great heights, we may make use of a series of kites of dif- 

 ferent sizes. t We first allow the largest sized kite to reach its great- 

 est height ; then, having attached its string to a second, but of less 

 size, we let it likewise ascend, its string being in its turn connected 

 to a third, and so on. This union of kites was used for the first time 

 by \Vilson| when engaged in his researches on the temperature of 

 elevated strata of air in 1749. The height to which the first kite 

 thus reached was very remarkable, since it could be frequently seen to 



'^ Comptes Rendus, tome X, page 712, 1840. 



f In bis experiments on atmos[)heric electricity, Cuthherison made use of tlirec kites com- 

 bined in tins manner, and the cords of whicb presented an entire length of 1,500 feet. 

 Bililiotlienue Britauni<iue, hjcienct'S et Arts, tome XXXIX, page US. Geneva, 1808. 



X Lehrbuch dcr Meteorol., by Koemtz, tome II, page 395. 



