to a great depth in the Sea. 145 



to every degree of pressure. Several were destroyed, but one 

 at thirty fathoms and another at eighty fathoms formed cu- 

 rious exceptions. They were cracked and half-filled with water, 

 but the water was effectually inclosed within them. Those that 

 came up entire contained not the least water. 



Two very strong bottles were then sent down, one to 140 

 fathoms, which came up quite empty, and the other to 120 fa- 

 thoms. This last admitted half a teaspoonful of water, but this 

 was between the stopper, as the same bottle, fresh secured, and 

 sent to the increased depth of 140 fathoms, came up unaflPected. 

 This last bottle, containing sixty-five square inches of surface, 

 must have suffered a pressure of at least ten tons. 



Now, as under every circumstance and under every pressure 

 (for mention is not made of half the number submitted to trial) 

 the glass vessels were either broken or cracked, or had receiv- 

 ed nothing, it is fair to conclude with Dr Green that glass is 

 impermeable. 



I would also remark, that the case of the hollow glass stop- 

 pers exhibits a singular proof of the great elasticity of glass ; 

 for they had under strong pressure admitted water through 

 those cracks, which so collapsed when that pressure was re- 

 moved as completely to retain that water. 



The cracked stoppers also, as they were but half filled, are 

 incontestable evidence of the manner in which bottles generally 

 are broken, not by being first filled, and then suffering from 

 the expansion of water when under less pressure, as Dr Green 

 seems to think, but by actual pressure from without. 



I might here subjoin that a soldered tin canister, as being 

 well calculated from its flexibility to show the manner in which 

 vessels were affected, was lowered to 100 fathoms. It was bul- 

 ged in and most severely compressed. 



I have the honour to be. Sir, your most obedient servant, 



Charles H. Weston. 



To Dr Brewster, F. R. S. &c. &c. 



VOL. X. NO. I. JAN. 1829. K 



