CORRESPONDENCE. Ill 



eel to think that this is entirely attributable to the difference of con- 

 traction in the base and stem of the instruments, from the variation 

 in the rate of cooling ; that in the sun being more rapid in its 

 transition than the other. 



I remain, Sir, yours, &c. 



J. Murray. 

 Hull, 22nd June, 1836. 



To the Editor of "The Analyst." 

 Sir, 



During a voyage across the Atlantic in the New York Packet 

 Ship, Roscoe — Captain Delano — our conversation one day happened 

 to turn on * the non-permeability of glass by water," when the 

 Captain very obligingly allowed me to copy the following notes from 

 his log-book ; which notes I have great pleasure in forwarding to 

 you, as they confirm the experiments made by Mr. Rudder, of which 

 a description is given in the 1 3th number of The Analyst. 



An experiment to ascertain the pressure of the sea, off the Isle of 

 France, 8th May, 1826, ship Florida :— 



1. A glass globe, bought for the purpose, was fastened to the lead- 

 line and sunk by three leads to the depth of 280 fathoms. 



2. On the same line, ]8 fathoms above the globe, I put a small 

 bottle with an air-tight glass stopper. 



3. Forty fathoms above this, a stout glass bottle, with a good cork 

 sealed and covered with three coats of linen dipped in hot pitch. 

 Each coat was allowed to cool before the other was put on. 



4. Thirty fathoms above this, another bottle was attached to the 

 line, much stouter and corked and sealed like the first, with only 

 one covering of cloth. 



5. Forty fathoms above this was a small bottle filled with fresh 

 water, well corked. 



6. Thirty fathoms from this an empty bottle, corked tight and 

 sealed, a sail-needle passed through the cork and projecting on both 

 sides. 



On hauling up the line 



The empty bottle (No. 6) with the sail-needle was half full of 

 water, and the cork and sealing as perfect as ever. 



The cork of the second (No. 5) was loose and raised a little, and 

 the fresh water a little brackish. 



