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LIV. Reply to Mr. J. de C. Sowerby's Remarks on " Experi- 

 ments on the Pressure of the Sea at considerable Depths" By 

 Jacob Green, M.D. Professor of Chemistry in Jefferson's 

 Medical College, Philadelphia, United States. 



To Richard Taylor, Esq. 



T N your valuable Magazine for July 1 828, there appeared some 

 -'- remarks made by me, " On the Pressure of the Sea at con- 

 siderable Depths ;" and in the next Number J. de C. Sowerby, 

 Esq. has favoured us with a kind of criticism on the commu- 

 nication. Now, although the subject is not a very important 

 one, still no person feels satisfied with having his statements 

 misrepresented, whether this be done through mere inadvert- 

 ence, or in any other manner ; I hope therefore you will allow 

 me a word in reply. 



The conclusion that I drew from my experiments was, " that 

 at the depth of 230 fathoms, the water enters glass vessels 

 through the stoppers and coverings which surround them, and 

 not through the pores of the glass :" — not that the fact, that 

 water will not penetrate glass at all, as Mr. S. says, has been 

 so often proved before, but merely that it will not at the depth 

 of 230 fathoms. Now if Mr. Sowerby had shown us that this 

 fact had ever been proved before, his remarks would have been 

 in point, and I should have thought my experiments of no 

 value. The fact, however, never could have been proved with- 

 out using a glass vessel hermetically sealed; and which, as far 

 as my knowledge extends, never was done before. Mr. S. 

 says, " Dr. Green thinks that by proving [as others have done) 

 that the water would not penetrate glass, he has reduced the 

 question to very narrow limits." Mr. S. should certainly have 

 given us his authorities here; and until they are produced 

 I shall consider my experiment as the first to settle the fact*. 



The misrepresentation to which I have alluded is, that Mr. S. 

 cites me as concluding that the water enters glass vessels 

 through the " cork and all its coverings, in consequence of the 

 vast pressure of superincumbent water, in the same manner as 

 blocks of woods are penetrated by mercury in the pneumatic 

 experiment of the mercurial shower." If any one will lake 



* In the Rev. Mr. Campbell's account of his second Missionary .loiirncy 

 in South Africa, published about seven years ago, nt the end of the second 

 volume, Dr. f ireen will find the particulars of an experiiiKiit made by 

 Mr. Campbell with two globular bottles hernietically scaled. They were 

 sunk to the perpendicular depth of 200 fathonu", and on being raised, they 

 were found empty; thus proving, that, at tliis depth at least, water will not 

 penetrate glass. — Edit. 



3 B 2 th 



