OBSERVATIONS ON WELLS. £9 



fatisfaclory reafon may be given for their reciprocation, which* 



though not contemporary with the ebbing and flowing of the 



tide, is yet fo far dependent upon it, as to follow it at an in- it refemfeles a 



terval of two hours, but in fuch a way that the immediate in- river tide, pro- 



r c duced on the 



jluence of the tide upon it only lalts about four hours out of the f re ft, water by 



twelve, notwithftanding the effect produced in that time re- t . hefe ^ : , . 

 quires nearly fix more to put the wells into their original ftate ] a , er . an dhas 

 of vacuity or reft. its ebb longer 



Laftly, the fame reafoning which accounts for the alternate If ^ ^ rea ™ * 

 riling and falling of the water in the artificial wells, makes it flowed down a 

 more than probable, that if the line of the natural fprings had jjj^'j* h?hcft 

 been below the low-water mark, the artificial wells would tide, the ftream 

 have been not only required to be deeper, but would have ^° uld alwa J s 

 been invariable in quantity ; alfo, that if the faid line had been 

 above high-water mark, it would have been in vain to have 

 dug for water into the rock above, whilft there continued a 

 natural iffue below : and fhould it be atked, why the water 

 that has an immediate communication occafionally with the fea 

 yet continues frejh, the fame anfwer may be given that will 

 apply in the cafe of frefti water being driven back to Chelfea 

 and Putney at every fucceffive tide that enters the mouth of 

 the Thames. 

 Parfon's Green, Aug. 29, 1 802. 



II. 



On the Theory of Gahanifm. By John Bo stock, M. D. 

 From the Author. 



JL HE following Paper contains fome remarks upon the elec- Galvanifm and 

 trical pile of Volta, principally made with a view to illuftrate ^^ r,cit y are 

 and confirm the theory of its action, which I propofed in my 

 former communication. 



1. With refpect to the nature of the agent producing the 

 phenomena of galvanifm, there can fcarcely remain any rea- 

 fonable doubt of its perfect identity with the electric fluid. 

 The apparent diflimilarity in the effects of an electrical ma- 

 chine and a galvanic pile has been fufliciently accounted for, 

 without fuppofing any thing eflentially different in their nature, 

 and we feem enabled by proper management to produce from 



either 



