Dr Davy on Atmospheric Electricity. 445 



He is of opinion that, if confirmed, they will prove the existence 

 of " a form of electrical current, which, both in quantity and in- 

 tensity, is exactly intermediate between those of the common 

 electrical machine and the voltaic pile."* Another view may be 

 taken. It may be said, that they seem to be in favour of atmo- 

 spheric electricity not being a simple and single power, but com- 

 pounded somewhat after the analogy of the solar ray, and of its 

 possessing even a principle peculiar to itself. 



This notion I throw out merely conjecturally at present : it 

 might be equally difficult to prove it correct or to refute it. At 

 present it seems most desirable to accumulate facts, waiting 

 for the time when, by means of extensive induction, we may 

 hope to be enabled to arrive at a satisfactory conclusion. But 

 whatever that conclusion ultimately may be, in the mean time it 

 hardly admits of a doubt, that what is called atmospheric electri- 

 city exercises a powerful influence both in the aerial regions and on 

 the surface of the earth ; and on the latter, perhaps, greater and 

 more constantly than has hitherto been supposed. The results 

 of the experiments I have described may warrant this inference 

 in regard to constancy of feeble effect ; and very many facts, well 

 established and universally known, especially the changes not un- 

 frequently witnessed in the cellar and the dairy during thunder- 

 storms, may be adduced in proof of its more energetic action, in 

 accordance with Mr Barry's results, as an agent of chemical 

 change. 



Font Pitt, Chatham, June 7. 1835. 



the discharge of the voltaic apparatus presently blackens the chloride of silver. 1 ' — 

 (Abstracts of the Philosophical Transactions, vol. ii. p. 121.) I have exposed this 

 compound moist, just made, to the intensely bright light of a succession of flashes 

 of very vivid lightning, during a thunder-storm by night of unusual violence, even 

 in Malta, and which lasted several hours, without the least change of its colour. If 

 the above statement, be correct (and it probably is, as Mr Brande, in 1819, was 

 senior Secretary of the Royal Society, by whom the abstracts of papers are I under- 

 stand generally made), we have here apparently another point of difference between 

 voltaic and atmospheric electricity. 

 * Phil. Trans. 1833, p. 43. 



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