Chap. 9- WATER- WORKS. 291 



red an abundance of Air to make a little Wa- 

 ter : And it may be a very reafonable Doubt, 

 whether the Hollows of any Rocks are large 

 enough to contain Quantity €nough of Air 

 to make Water run fo continually, and in fuch 

 great Quantities, as we often fee them do. 



The ingenious Mr. Halley^ in his DiiTer- 

 tation on this Subjeft, in the Philof. Travf. 

 oi Jan. and Feb. 1692, feems to hint they are 

 deriv'd from Vapours exhal'd from the Sea 5 

 as does Monf. k Clerc^ in his Phyficks^ quo- 

 ting the aforefaid Author, in Juftification of 

 his Opinion. Againft fuch great Authority, I 

 fliall not pretend abfolutely to determine 5 

 the flrefs of the Argument there, is, that the 

 quantity of Vapours drawn out of the Ocean, 

 by the Heat of the Sun, (efpecially amongft 

 the Tropicks) is fo great, that it put his 

 Aftronomical Inftruments in diforder ^ and 

 particularly, that his Paper was in a very 

 fliort fpace of Time fo wet, that it would 

 not hold Ink. Thefe Obfervations were made 

 not only in Europe^ but in the Ifland of Saint 

 Helen 3 to all which he adds, and inferrs from 

 thence, that thefe Vapours are difpers'd Qua- 

 quaverum by Winds) and that they lodge on 

 the higheft Hills, rather than below, there 

 finking down to the Receptacle or Fountain, 

 and afterwards break out in the manner we fee 

 them. 



It would certainly very much have con-^ 



firmed this Experiment, if they had at the 



fame time opend the Ground with any 



U 2 Inftru- 



