On a neuo Method of taking Deep Soundings in the Ocean. 185 



the flame is essential to the result, in the other case the air 

 presents only an obstacle to be removed, and the experiment 

 will succeed better in a vacuum. 



It has only been on the authority of numerous and often- 

 repeated experiments that I have thus ventured to dissent from 

 the conclusion of the eminent philosopher by whose profound 

 and varied researches the science of electricity has of late years 

 been so much extended. Nor is the important question of the 

 identity of common and voltaic electricity affected by the re- 

 sults which I have obtained. The similarity of the arch formed 

 by the discharge of an electrical and galvanic battery between 

 charcoal surfaces shows clearly that there is a perfect analogy 

 in the passage of the voltaic and common electric currents 

 across air. 



Belfast, June 22, 1836. 



XXXIX. On a ne'w Method of taking Deep Sou?idings in the 

 Ocean. By A Correspondent.* 



'T'HE tediousness which attends the taking soundings in the 

 -■■ ocean by the common method with the deep-sea lead, and 

 the impossibility of thus ascertaining depths beyond a certain 

 very limited extent, has led to the invention of different in- 

 struments which can assist in the operation. These machines 

 descend alone through the water, and on reaching the ground 

 are freed from the weight that dragged them to the bottom ; 

 when, rising to the surface, they bring with them an exact 

 account of the depth to which they have gone. It is not diffi- 

 cult to suspend the balance weight so that it shall be detached 

 by the shock against the ground from the rest of the apparatus, 

 and allow it, if itself buoyant, to regain the surface: nor is it 

 less easy to adapt a rotator, whose vanes shall be moved by the 

 current during the descent, and thus cause the revolution of 

 the index which registers on a dial-plate tlie fathoms of depth. 

 But the great difficulty is to give the machine that buoyancy 

 requisite to bring it back however deep it may have sunk. 

 Mr. Massey, who has practically applied this invention, used 

 a hollow copper globe filled with air : this could not be made 

 very strong consistently with the necessary lightness; and he 

 found that the instrument, which answered well in a depth of 

 two hundred fathoms, when let go in water of unknown deep- 

 ness never appeared again. On repeating the experiment with a 

 new machine inclosed in a net and attached to a line, by which 

 it was drawn back from four hundred fathoms, it was evident 



• Communicated hy the Author. See on tills subject Lontl. and Edinb. 

 Phil. Mag., vol. ill. pp. 82, :{.'.2. 



Third Series. Vol.9. No. 53. S^;j/. 1836. X 



