Mr. W. S. Harris on Lightning Conductors. SI 3 



© 



generation : he has observed the devolopment and departure of suc- 

 cessive families, and perceives that the defunct are devoured by 

 their survivors. On the 20th of July, 1842, he terminated the ex- 

 periment with the sulphate battery, and was so unfortunate as not 

 to secure a single specimen of the insect. With respect to the 

 spongy aggregations around the positive electrode, he has found 

 they are not, as he anticipated, pure silicon, but apparently an in- 

 ferior oxide of that element. He quotes Dr. Brown's opinion, that 

 " it may throw light on the doubtful question of the atomic weight 

 of silicon." 



2nd. " Observations by W. Snow Harris, Esq., F.R.S., on a paper 

 by Charles V. Walker, Esq., Hon. Sec. L.E.S., entitled ' On the 

 Action of Lightning Conductors.' " 



The author of this paper does not agree with Mr. Walker in 

 fearing danger from the passage of a spark from the lightning-rod 

 to a vicinal conducting body; and he thinks, contrary to Mr. 

 Walker, that the discharge of a Leyden jar does resemble a flash 

 of lightning. He says, that " the lightning-rod, so far from send- 

 ing out sparks to neighbouring bodies, directs the passing charge 

 from them altogether." He states, that " when a great variety 

 of circuits are open to a passing discharge of electricity or light- 

 ning, the charge will be likely to divide on them all ;" and that 

 this is by no means a new fact : this he alludes to as the divi- 

 sion of charge. He adds, that it will not go off to semi-insulated 

 bodies ; and this he appears to consider " lateral discharge." He 

 then proceeds to analyse Mr. Walker's experiments, which had in- 

 duced the latter gentleman to doubt the analogy between Leyden 

 and lightning discharges, and allows the distinction between the two 

 cases, but not the difference. He conceives that the difference in 

 the direction of the discharge does not operate against its special 

 character. With respect to the difference in the length of spark, 

 he considers this as " altogether an affair of intensity, and of the 

 form and disposition of the charged conductors ;" and proceeds to 

 show varied phenomena, in connection with varied form and ar- 

 rangement. He does not place so much reliance as Mr. Walker 

 upon experiments from the prime conductor, but allows certain gene- 

 ral points in which it does resemble a charged cloud. He then ex- 

 amines the experiments which were made with the prime conductor 

 of the Polytechnic Institution, and shows in what respects he is 

 unwilling to receive them. He concludes with expressing a conviction 

 that there is no danger of lightning leaving a conductor to enter 

 vicinal bodies ; and hence considers that Mr. Walker's suggestions 

 relative to connecting these bodies with the main rod, are not needed. 



Mr. Weekes's Electro-Meteorological Register for August was 

 then laid before the Society. - 



CHEMICAL SOCIETY. 

 [Continued from vol. xx. p. 344.] 

 Dec. 21, 1841 . — The following communications were read : — 

 " On the Agency of Caloric in permanently modifying the state 



