3 54 Cautions againjl tie Fear of Lightning. [Book IV. 



75,420 leagues in a fecond of time, its effects may be 

 confidered as inftantaneous within any moderate dif- 

 tance. Sound, on the contrary, is tranfmitted only at 

 the rate of 1,142 feet, or about 380 yards in a fecond. 

 By accurately obferving therefore the time which in- 

 tervenes between the flafh and the noife of thunder 

 which follows it, a very near calculation may be made 

 of its diftance, and I know no better means of remov- 

 ing unneceffary apprehenfions. 



The fuccefs of Dr. Franklin, in afcertaining the 

 caufe of thunder and lightning, induced fucceeding 

 philofophers to apply the fame theory to the expla- 

 nation of the other atmofpherical phenomena. From 

 a number of obfervations, the indefatigable Beccaria 

 endeavours to account for the rifing of vapours and 

 the fall of rain, upon electrical principles ; and, ic 

 mud be confefied, that if it is not a primary agent in 

 thefe effects, it would be rafhnefs entirely to deny its 

 influence. This philofopher fuppofes, that previous 

 to rain a quantity of electric matter efcapes from the 

 earth, and in its afcent to the higher regions of the 

 air collects and conducts into its path a great quan- 

 tity of vapours. The fame caufe that collects will 

 condenfe them more and more, till in the places of the 

 neareft intervals they come almoft into contact, fo as 

 to form fmall drops, which, uniting with others as 

 they fall, come down in rain. The rain he fuppofes 

 to fall heavier in proportion as the electricity is more 

 vigorous. 



Hail, he fuppofes to be formed in the higher regions 

 of air, where the cold is intenie, and where the elec- 

 tric matter is very copious. In thefe ' circumflances, 

 a great number of particles of water are brought near 

 together, where they are frozen, and in their defcent 

 collect other particles j fo that the denfity of the fub- 

 ftancc of the hail-ftone grows lefs and lefs from the 

 9 center, 



