Mr. T. S. Davies on Geometry and Geometers. 497 



to depend, at present, as little as possible on the mechanical 

 violence of ths drops of water; because some experiments, not 

 yet fit for publication, seem to show that when steam and air 

 at the same temperature are discharged into the atmosphere, 

 the amount of water simultaneously discharged may be greatly 

 reduced, perhaps to nothing, 



69. The negative state of the air, which one would expect to 

 find particular!}' strong just after a thunder-storm, may slowly 

 discharge itself on the earth by conduction, or on the clouds, 

 or rain, and thus to the earth by convection; nevertheless the 

 direct tendency of lightning, according to this theory, is to 

 render the upper regions negative ; and the facilities for the 

 return of this negative charge to the earth will decrease in 

 some proportion as the altitude increases. The continual 

 thunder-storms of the hotter climates may therefore gradually 

 accumulate a powerful negative charge in the heavens. Sup- 

 pose now, when the air is thus highly charged, that a co- 

 lumn of mist sufficiently high and dense to act the part of an 

 electric conductor to the positive earth and negative heavens 

 should be interposed between them, the electricity would then 

 pass as a series of disruptive discharges, and would, I suppose, 

 be the aurora. 



7 Prospect Place, Ball's J*oncl Road, 

 3rd December 1849. 



LXII. Geometry and Geometers. Collected hy T. Sr Davjes, 

 Esq., F.R.S. and F.S.A.^ 



No. IV. 



'T'HE printing of the three letters of John Bernoulli to 

 ■* Cramer, which I had designed to give as the next of 

 this series of " gossipings," must be deferred for awhile; as, 

 from particular considerations, I am led to think it desirable 

 to confine myself, for the present at least, to matters of more 

 purely English interest. 



In 1747 Mr. Thomas Simpson published the first edition 

 of his Elements of Geometry; and in 1756 Dr. Simson the 

 first edition of his Euclid. In this latter work are two notes 

 upon objections which had been raised in the former, to some 

 of Euclid's processes. In 1760 Mr. Simpson published the 

 second edition of his Elements, in which he defends himself 

 with great earnestness on those topics; and Dr. Hutton (in 

 his Life of Simpson, prefixed to the Select Exercises, ed. of 



♦ Cominunicated by the Author. 

 Phil. Mag. S. 3. No. 239. Siippl. Vol. 35. 2 K 



