General Science. 367 



pores of the glass. This opinion is contradicted by the following experi- 

 ments made by Dr Green of Philadelphia. 



" A hollow glass globe hermetically sealed, which I had previously 

 prepared in Philadelphia, was then fastened to a line, and sunk, with 

 a heavy mass of lead, to the depth of 230 fathoms, or 1380 feet. On 

 the same line, and 30 fathoms above the glass globe, was fastened a small 

 bottle with an air-tight glass stopper ; 50 fathoms above this, a stout glass 

 bottle with a long neck was tied ; a good cork was previously driven into 

 the mouth of this bottle, which was then sealed over with pitch, and a 

 piece of linen dipped in melted pitch was placed over this ; and when 

 cool, another piece of linen treated in the same way was fastened over the 

 first. Twenty fathoms above this bottle, another was attached to the line, 

 much stouter, and corked and sealed like the first, except that it had but 

 one covering of pitched sail-cloth. Thirty fathoms above this was a small 

 thin bottle filled with fresh water closely corked: and twenty fathoms 

 from this last there was a thin empty bottle corked tight and sealed, a 

 sail-needle being passed through and through the cork, so as to project on 

 either side of the neck. 



" Upon drawing in the line, thus furnished with its vessels, and which 

 appeared to have sunk in a perpendicular direction, the following was the 

 result : 



" The empty bottle with the sail-needle through the cork, and which 

 came up the first, was about half full of water, and the cork and sealing 

 as perfect as when it first entered the sea. 



" The cork of the second bottle, which had been previously filled with 

 fresh water, was loosened and a little raised, and the water was brackish, 



" The third bottle, which was sealed and covered with a single piece of 

 sail-cloth, came up empty, and in all respects as it descended. 



" The fourth bottle, with a long neck, and the cork of which was se- 

 cured with two layers of linen, was crushed to pieces, all except that part 

 of the neck round which the line was tied ; the neck of the bottle both 

 above and below the place where the line was fastened had disappeared, 

 and the intermediate portion remained embraced by the line. This I 

 thought a little remarkable ; and perhaps may be explained by supposing 

 that the bottle was first filled by the superincumbent pressure with dense 

 sea- water, which expanded on being drawn up near the surface. Had the 

 vessel been broken by external pressure, that part surrounded with the 

 line ought to have been crushed with the rest. 



" The fifth bottle, which had been made for the purpose of containing 

 French perfumery or ether, and which was therefore furnished with a 

 long close glass-stopper, came up about one-fourth filled with water. 



i( The hollow glass-globe, hermetically sealed, which was the last and 

 had been sunk the deepest of all, was found perfectly empty, not having 

 suffered the smallest change. It is therefore concluded, 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. 



