410 Quetelet on the Electricity of the Air. 



its intensity is greater in the north than in the south, although 

 if the upper stratum of the air is not so high, the electricity 

 must be stronger, as seems to be shown by the auroras. 

 " The earth is generally regarded as solid throughout all its 

 extent, although many physicists consider that it is only solid 

 in its exterior portion. They say, and as we think with reason, 

 that the interior portion, in a state of greater or less fluidity, 

 may have its own movements, which may occasion magnetic 

 variations, and also the electric variations that are intimately 

 connected with them." 



The great laws of the distribution of atmospheric electricity 

 are often masked by secondary causes. Thus, especially during- 

 the summer, we notice the formation of strata of clouds car- 

 rying an electricity which M. Quetelet denominates accidental, 

 and which gives rise to storms. " These clouds may be the 

 origin of hail, which finds itself attracted and repelled by the 

 upper stratum of the air, until it falls by force of gravity/'' or 

 there may be a direct electrical action upon the earth in the shape 

 of storms. Negative electricity is more frequent in the atmo- 

 sphere during the summer, the space between the earth and 

 the stationary portion of the atmosphere being then greater, 

 and also being drier and better able to accommodate clouds 

 which assume "a supplementary electricity." The tranquil 

 passage of electricity towards the earth is more frequent in 

 winter, but in the summer, by reason of the greater dryness, it 

 is less continuous and more violent. Thunder-storms are more 

 common in summer than in winter, but those of the latter sea- 

 son are often extremely dangerous. One, for example, in the 

 winter of 1860, struck twenty clock towers within the limits of 

 Belgium, and in the course of a few hours ; and in the night of 

 April 14th, 1718, twenty-four towers were struck in France, 

 along the coasts of Brittany. Summer storms are usually less 

 destructive on the surface of the earth, and their action limited 

 to a smaller space. Winter storms act over a wider range. 



M. Quetelet gives numerous details of the great storm of 

 the 19th February, 1860, to which allusion has just been made, 

 and which surpassed in violence any ever known to have 

 occurred in Belgium. It began on the evening of the Sunday 

 in question, and followed the route usually taken by such 

 scourges in that country. About seven o' clock it burst over 

 Rolleghem and Courtroy ; an hour afterwards it reached Ghent, 

 Brussels, and the neighbourhood of Antwerp ; and by nine it 

 was at Liege, carrying devastation as it went, and increasing 

 in force. Hail, rain, and snow fell at various places during its 

 passage, several of the churches upon winch the lightning fell 

 were set on fire ; the wind was tempestuous, and the thunder- 

 peals extremely loud. The barometer was strongly depressed, 



