392 PHILOSOPHICAL TRANSACTIONS. [aNNO I759. 



that of thunder. But this hypothesis having gained no credit, we need not em- 

 ploy time in refuting it; and the less now, as the nature of lightning is so much 

 better understood than when this theory was first published. It may only be 

 observed, that before the matter of lightning was discovered to be of the electri- 

 cal kind, it was natural to suppose it to be formed of the sulphureous vapours 

 arising from the earth ; and if the earth was found proper for producing such ex^ 

 halations, of course it was judged capable of furnishing materials for all the lucid 

 phenomena in the ethereal regions. Thus, not a hundred years ago, the comets 

 themselves were accounted for on no better principle; and therefore we are the 

 less to wonder if these meteors have been hitherto almost constantly referred, 

 even by the best naturalists, to the same origin. 



If it is then probable that these balls of fire come from regions far beyond the 

 reach of our vapours; if they approach often so near to the earth, and so seldom 

 or never touch it ; if they are moved with so much celerity, as in that respect to 

 have the character of celestial bodies ; if they are seen flying in all directions, and 

 consequently have a motion of their own, independent of that of our globe; if they 

 part with such quantities of an elastic fluid, a phlogistic matter, and probably an 

 acid, surely we are not to consider them as indifferent to us, much less as for- 

 tuitous masses, or trains of terrestrial exhalations in the ethereal regions ; but 

 rather as bodies of a nobler origin, possibly revolving about some centre, formed 

 and regulated by the Creator for wise and beneficent purposes, even with regard 

 to our atmosphere ; which, during their combustion, they may supply with some 

 subtile and salutary matter, or remove from it such parts as begin to be super- 

 fluous, or noxious to the inhabitants of the earth. 



XXVI 11. Thoughts on the different Impregnation oj Mineral Waters-, more par- 

 ticularly on the Existence of Sulphur in some of them. By John Rulty, M. D. 

 p. 275. 



It would be useless in the present advanced state of chemical knowledge re- 

 specting the different impregnation of mineral waters, to reprint this paper. 



XXIX. On the Effects of a Storm of Thunder and Lightning at Rickmansworthy 

 in Hertfordshire, July l6, 17 5Q. In a Letter from Mrs. Ann M'hitfeld, 

 Communicated by Mr. John Van Rixtel, F. R. S. p. 282. 



One of those common effects of a house struck by lightning. A stack of 

 chimneys and some tiles carried off the roof. Some windows forced in, several 

 things within the house broken, the rooms filled with dust and sulphureous 

 smell, &c. 



