164 



SCIENCE. 



[Vol. IV., No. 82. 



ATMOSPHERIC ELECTRICITY. 



At the present time there is no satisfactory 

 theory of the source of atmospheric electricit}^. 

 Many believe, in the absence of positive evi- 

 dence of the production of electricit} r b} T the 

 operation of evaporation and condensation, 

 that the earth has a definite charge, which 

 resulted from the operations at its birth, and 

 which it has kept undiminished in amount ; 

 and that thunder-storms are merely the expres- 

 sion of local accumulation due to currents of 

 air. 



Mr. G. Le Goarant de Tromelin, in a late 

 number of the Comptes rendus, advances the 

 opinion that atmospheric electricity is due to 

 the friction of the air, humid or dry, upon 

 the surface of land or water, and calls atten- 

 tion to Armstrong's hydro- electric machine, 

 which produced electricity of high tension by 

 the friction of jets of steam in issuing from 

 narrow orifices. According to Tromelin, the 

 wind, in skimming over the surface of water, 

 carries water from the crests of the waves, 

 which pla} T the part of the comb of Armstrong's 

 machine. The roughness of the soil does the 

 same on land when a damp wind passes over 

 it. The charge thus produced is collected upon 

 the vesicles of clouds. The potential energy 

 of a cloud depends upon its configuration and 

 its temperature. If this configuration changes 

 under the effect of condensation or congelation 

 of the aqueous particles, the cloud absorbs a 

 certain amount of energj^, which must be found 

 again under the form of an augmentation of 

 potential energ} T : hence there is an electrical 

 interchange constantly going on in the cloud 

 region of the air ; and when these changes are 

 rapid, and great in amount, we have thunder- 

 storms and other great electrical manifesta- 

 tions. 



The advocates of Mr. Tromelin' s views can 

 point to the effect of the blasts of sand driven 

 b} T the wind upon the p}Tamids, and to the 

 extraordinary electrical manifestations upon 

 high peaks in Colorado, where every aiguille 

 seems to hiss, at times, with the escaping elec- 

 trical charge. 



We believe that the time has arrived when 

 the scientific world no longer looks upon 

 electrical phenomena as isolated and separate 

 from the phenomena of heat and light, or 

 chemical reactions. We cannot believe that 

 any change can take place in the arrange- 

 ment and mutual attractions of molecules 

 without electrical manifestations. If we are 

 to have a thermal chemistry, we must also 

 have an electrical chemistry ; and the history 



of the energy of a chemical reaction is not 

 completely told when we sum up the heat of 

 this reaction, unless we count also the heat- 

 equivalent of the resulting electrical changes. 

 If we were, therefore, to frame a theory of 

 atmospheric electricity, we should begin it 

 with the assertion that every change in the 

 configuration or arrangement of particles of 

 matter is accompanied by an electrical dis- 

 turbance ; and, as far as this assertion goes, 

 all the present theories of atmospheric elec- 

 tricity would fall under it as special cases. 



The object of this paper, however, is not 

 to frame hypotheses, but to trace the recent 

 work which has been done in systematic 

 observation of atmospheric electricity. It is 

 only to systematic observation that we can 

 evidently look for information which will be 

 of immediate practical value to our signal- 

 service. Unfortunately, no s}^stematic obser- 

 vations have been made for any length of time 

 in an}^ country. 



The electrical conference at Paris, held last 

 April, was adjourned from a meeting of the 

 previous year ; and committees were appointed 

 to study the subject of atmospheric electricity 

 and earth-currents in different countries. The 

 time was evidently too short for such a stu- 

 pendous undertaking ; but the conference did 

 valuable work in stimulating sj^stematic obser- 

 vation, and creating a bureau at Berne, to 

 which it was recommended that observations 

 made in different countries should be sent. 

 The agitation of the subject of such observa- 

 tions called forth several papers. Professor 

 Eoiti of Florence presented to the conference 

 the result of observations made through sev- 

 eral months with a self-registering apparatus. 

 He found that the zero of Mascart's electrom- 

 eter changed from time to time, and traced 

 this change to the mechanical effect of the 

 sulphuric acid upon the platinum wire con- 

 nected with the electrometer needle. He 

 therefore dispensed with the Leyden jar of the 

 Thomson and the Mascart electrometer, and 

 suspended the needle by a very fine silver wire 

 which was connected directly to the positive 

 pole of a water-battery of many cells. This 

 instrument was found to work well. Professor 

 Roiti believes that local disturbances have 

 great effect, and that these local effects must 

 be carefully taken into account in comparing 

 simultaneous observations over large areas. 



Athough the scientific world has generally 

 accepted Thomson's quadrant electrometer, or 

 some modification of it (like that of Mascart's 

 or Clifton's), as the most suitable instrument 

 for the observation of atmospheric electricity, 



