74 ON THE NON-PERMEABILITY OF GLASS BY WATER. 



Two Other bottles were prepared in a similar manner, with the 

 exception of the lead caps, and were sunk to a depth of 102 fa- 

 thoms. These bottles were filled with water, and the corks which, 

 previous to immersion, stood nearly half an inch above the necks of 

 the bottles, had been so much compressed as to allow the water to 

 pass round them. One of the corks exhibited this compresssed ap- 

 pearance for a length of time after it was drawn up, leaving the 

 pitch standing like a wall above the neck of the bottle. 



The next experiment was made in the jolly boat, at some distance 

 from the ship, as on former occasions ; when three bottles were sunk 

 to the depth of 150 fathoms, and, consequently, subjected to a pres- 

 sure of about 450 pounds on the square inch. When drawn up, it 

 was discovered that Mr, Benson's bottle was full of water, and Mr. 

 Rudder's perfectly free from all fluid. The bottle sunk by Mr. 

 Benson was prepared by placing a wooden stay within the bottle, 

 as shewn in figure 4, upon which a cork was firmly driven. The 

 neck of the bottle was then filled with melted pitch, into which a 

 cork was forced down ; over the whole was tied a piece of leather, 

 and the neck of the bottle immersed in pitch. Mr. Rudder's first 

 bottle was prepared in a similar manner to Mr. Benson's, excepting 

 that the cork was cut ofl* flush with the neck of the bottle (which, 

 being patent, was consequently true), and, after being dipped in 

 boiling pitch, a halfpenny was imbedded upon the top of the cork. 

 The second bottle had the wooden stay for support to the cork, fixed 

 perpendicularly ; and over the above-described stopping a cap of 

 lead, of about one-eighth of an inch in thickness, was secured, and 

 pitched over, excepting on the upper surface of the lead. The ap- 

 pearance of the respective bottles, when drawn up, was as follows : 

 Mr. Benson's bottle had the corks and their covering so compressed 

 that they were nearly three quarters of an inch below the rim of the 

 neck, and the bottle as full of water as bottles usually are of wine. 

 The air in the neck of the bottle, which must have been highly 

 compressed, continued to issue through the pores of the cork for a 

 considerable time after the bottle had been drawn up. In Mr. 

 Rudder's first bottle no alteration was apparent ; and in the second 

 the only change that had taken place was the compression of the 

 lead inwards, forming a concavity, of about one-fourth of an inch in 

 depth, in the centre. 



