OPTICAL PHENOMENA. 517 



the cattle gather lowing to a covert the eagle nestles in the cleft of the rock with 

 folded wings the hart looks wild and anxious : only the poor seal seems to experience 

 agreeable sensations, for he will come out of his hiding-place in the deep, at the call of 

 the thunder, and repose upon some overhanging ledge, as if calmly enjoying the convulsion 

 of the elements. 



Since the month of June 1752, when Franklin performed the celebrated kite experi- 

 ment, by which he became the modern Prometheus, bringing down the celestial fire to the 

 earth, the identity of lightning and electricity has been universally known. The theory 

 of the electric fluid, as it is called, is to be sought for in philosophical treatises, our 

 province being to notice its distribution, phenomena, and effects. That subtle principle 

 which the Greeks denominated electricity, from i/XeKTjoov, amber, because the property was 

 first noticed in that substance, appears to be a universally diffused agent, its presence 

 having been detected in connection with the clouds, with hail, rain, and snow, with vege- 

 tation, animals, and the interior strata of the earth. But undue accumulation transpires 

 the electrical equilibrium is disturbed ; and the resulting phenomena of equalisation 

 are lightning and thunder. Thus two clouds, or a cloud and the earth, unequally electrified, 

 tend to return to a condition of equality through a conducting medium, a metallic or moist 

 body having the preference as a conductor, the discharge of electricity appearing in the 

 form of a spark or flash, accompanied by a loud detonation according to its violence, the 

 peal rebounding in echoes from cloud to cloud, and from hill to hill. Some regions of the 

 globe are peculiarly subject to accumulations of electricity. Mr. Hamilton, in his work on 

 Asia Minor, observes : " One of the most remarkable phenomena which I observed in 

 Angora, was the great degree of electricity which seemed to pervade everything. I 

 observed it particularly in silk handkerchiefs, linen and woollen stuffs. At times, when I 

 went to bed in the dark, the sparks which were emitted from the blanket gave it the 

 appearance of a sheet of fire ; when I took up a silk handkerchief, the crackling noise 

 would resemble that of breaking a handful of dried leaves or grass ; and on one or two 

 occasions I clearly felt my hands and fingers tingle from the electric fluid. I could only 

 attribute it to the extreme dryness of the atmosphere, and momentary friction. I did 

 not observe that it was at all influenced by wind ; the phenomena were the same, whether 

 by night or by day, in wind or calm. Not a cloud was visible during the whole of my 

 stay." Similar striking indications of the prevalence of electric action have frequently 

 been observed by travellers when near the summits of high mountains, as by SirW. 

 J. Hooker on Ben Nevis, Saussure on Mont Blanc, and Tupper on Mount Etna. The 

 latter, descending a field of snow, a good conductor, felt a slight shock upon entering a 

 cloud which seemed electric, with a sensation of pain in the back. The hair of his head 

 stood erect, and upon moving the hand near the head, a humming sound proceeded from 

 it, which arose from a succession of sparks. Though a situation of great danger, yet we 

 have several instances of such clouds having been traversed with impunity, when in the act 

 of electrical explosion. The Abbe Richard, in August 1778, passed through a thunder- 

 cloud on the small mountain called Boyer, between Chalons and Tournus. Before he entered 

 the cloud, the thunder sounded, as it is wont to do, with a prolonged reverberation ; but 

 when enveloped in it, only single peals were heard, with intervals of silence, without any 

 roll ; and after he had passed above the cloud, it reverberated as before, and the lightning 

 flashed. The sister of M. Arago was a party to a similar occurrence between Estagel 

 and Limoux, and some officers of engineers likewise, during a trigonometrical survey on 

 the Pyrenees. 



The energy of atmospheric electricity appears to decrease as we recede from the 

 equator to the poles, thus sympathizing with light and heat ; for it is in tropical countries 

 that the most terrific flashes of lightning and the loudest bursts of heaven's artillery 



LL 3 



