ELECTRICITY. 



storm. 



7 feet tn length. These great flashes were spontnne- 

 ou, and in spite of the abund.uu-c ut tire which they 

 formed, they constantly t'i-11 upon the nearest non-electric 

 body. This circumstance inspirtd M. Homo* with con- 

 fidence, and lie did nut hf>itute to c\rite tin 1 lire with 

 hi discharging rod, at the time when tin- -torm wag 

 1 when tin' glass of which it was coin- 

 was two feet long, he was able to conduct, with- 

 : feeling the slightest shock, beams of fire (> and 7 

 lert long, with as much facility ns he formerly condiu ted 

 those which were scarcely 7 or 8 inches. In this expe- 

 rinoent, the string of the kite was one half longer than 

 it was in his other experiment ; and he attributes the 

 magnitude of the effects to the three following causes : 

 i the great length of the string. 2. To the con- 

 tinuity of the metallic wire which the string was wrap- 

 ped round. And, S. To the peculiar disposition of the 

 cloittlg. 



The identity of electricity being thus established by 

 numerous and direct experiments, philosophers next 

 attempted to observe the phenomena which accompa- 

 nied the production of thunder and lightning, and to 

 ascertain the manner in which they were generated by 

 the electricity of the atmosphere. 



Description \Vhcn the sky is clear and serene, low and dense 

 of a thunder clouds begin to form in the atmosphere. They are 

 spread over the heavens by a wind more or less violent, 

 and are succeeded by others more thick and obscure. 

 These clouds are agitated with various motions. While 

 some of them are moving above in one direction, 

 others are moving below them in an opposite direction. 

 One cloud is seen to attract another, while others 

 are separated by a repulsive force, and, in the midst of 

 this universal agitation, other clouds are resting im- 

 moveable, in virtue of the opposing forces with which 

 they are influenced. Amidst this conflict of opposite 

 forces, flashes of blue light are seen to dart with incon- 

 ceivable rapidity from one cloud to another, and, after 

 the lapse of several seconds, the rumbling noise of dis- 

 tant thunder is faintly distinguished. The sky soon 

 becomes more obscure, the lightning more frequent and 

 vivid, and the thunder more loud, and succeeding the 

 flashes of lightning at a shorter interval. A dread- 

 ful gloom is now spread over nature, and the sun 

 almost seems to threaten the extinction of his feeble 

 light The husbandman retires from the field*; the fish- 

 erman forsakes his nets ; the birds of the air desert 

 their native element ; the brute creation run up anil 

 down in wild dismay, or seek for shelter from the im- 

 pending danger ; and the sky and the fields are thus 

 left unpeopled during this dreadful strife of the ele- 

 ments. The storm is now at its height, the accumula- 

 ted electricity of the clouds is seen to strike towards the 

 earth, shivering the strongest oak in its passage. Sur- 

 rounded with actual danger, man himself begins to par- 

 take in the general dread, and amid this play of celestial 

 artillery, he often feels for the first time the true rank 

 which he holds in the scale of being. These tremen- 

 dous phenomena often make the circuit of the whole 

 horizon, and are frequently interrupted by heavy show- 

 >! of rain or hail, till the atmosphere resumes its 

 wonted serenity. 



The lesser phenomena which appear in a storm, do 



not merit any particular description. The flashes of 

 lightning sometimes appear of an angular or zigsag 

 form, and is then called forked lightning. At other 

 times, particularly when it strik rth, it has On 



the appearance of a dense globe of fire ; and at other J"? 

 times it is a sudden and universal flash, which has ^ 

 received the name of sheet lightning. 'I 

 lightning in most frequently seen in fine summer 

 evenings, and is on these occasions never accompanied 

 with thunder. The colour of lightning is sometimes of lu colour. 

 various shades of blue, at other times of a vivid yellow 

 colour, and at other times of a pale straw colour ; and 

 it is probable, that the nature and intensity of its colour 

 depends on the nature and density of the stratum of uir 

 which it traverse*. 



The noise of the thunder, which in general follows Sound of the 

 the flash of lightning, has various characters, depend- thunder, 

 ing on the situation of the person who hears it, and 

 probably on the state of the clouds in which it is pro- 

 duced. Sometimes it resembles a sudden crash, like tin- 

 sound of a piece of artillery, which is not repeated or 

 prolonged by reflection. Sometimes the noise is rum- 

 bling and irregular, like the prolonged and dying 

 echoes of a pistol when discharged in a mountainous 

 country ; and at other times it resembles the series of 

 sounds, which are produced by the successive discharge 

 of a great number of muskets. The first of these sounds 

 generally takes place when the thunder is near, and 

 has struck the ground ; and the second is generally the 

 character of distant thunder. The distance of the thun- 

 der stroke may be easily computed, by multiplying 1 142 

 by the number of seconds which elapse between the 

 flash and the thunder ; the product is the number of 

 feet at which the stroke has taken place. 



In the preceding observations, we have spoken only Q,, ^ ets 

 of that kind of lightning which either flashes from ccmling 

 cloud to cloud, or descends in a thunder bolt to the thunder- 

 earth, destroying every non-conducting body that resists bolt- 

 its passage. Another kind of thunderbolt, however, 

 has been observed, which rises from the earth, and has 

 therefore received the name of the ascending thunder- 

 bolt. This species of thunder appears to have been 

 observed by the ancients ; and the Tuscans have even 

 divided thunder into two kinds, viz. celestial and ter- 

 restrial, or that which falls from the clouds and that 

 which rises from the earth. * The first modem writer 

 who noticed this species of thunderbolt was the Mar- 

 quis de Mallei, who wrote a letter on the subject on 

 the 10th Sept. 1713 to M. Vallisnicri, professor in the 

 university of Padua. When living at the chateau of 

 Fosdinovo, situated on a mountain, he observed in the 

 time of a storm the lightning issue from the ground, at- 

 tended with a loud noise. The Abbe Jerome Lioni de 

 C'enedat witnessed the very same phenomenon in a vio- 

 lent thunder storm. A brilliant flame rose rapidly 

 from the earth to the height of two yards, and disap- 

 peared with a loud noise. 



George Frederick Richter J relates, that in the cel- 

 lar of the Benedictines of Fotigno, when the servants 

 were pouring into a cask some w ine which had been 

 boiled, a light flame shone round the funnel, and the 

 operation was scarcely finished, when a frightful noise, 

 similar to that of loud 'thunder, was heard. The eellarwas 

 filled with lire, the bottom of the cask was found pierced 



" Ktniria enimperc terra quoqiic fulmir.s arbittatur. " PHn. Hist. Nat. lib. ix. cap. 33. 



f- " Subilo actcncli flatnmam vindisMmam cunspicio, duo* paulo minus cubito tupra terrain tenui tractu ucendcntcm, et citius quom Mr-, 

 roevanescuitun, nlino tvrribili-sima fragore." Journal de Vcnise, torn, xxxii. art 8. 41. 

 $ Richter Dt naluiihu fulmtaum tractatuj plij/iiau. Leips. 1725. 



