130 JVatural History of the Ocean, fyc. 



and in N. Lat. 66°-l .0259, according to Scoresby : but 1 .020, 

 according to Capt. Ross. 



2. The sp. gr. increases with the depth from which it is 

 drawn. 



3. The Mediterranean sea has a greater sp. gr. than the 

 Atlantic. 



4. The water of the Bahic has a less sp. gr. than the At- 

 lantic, being 1.014. 



Capt. Scoresby found that the uniformity in the increas- 

 ing density of ocean waters, was interrupted by the influ- 

 ence of ice. 



The 2nd inference is from many experiments on sea wa- 

 ter drawn from different depths, and which were found uni- 

 form, except when interrupted by partial currents or the 

 influence of ice. The density increasing with the depth of 

 the ocean, Dr. Brewster attributes to the " imperfect elas- 

 ticity of water, preventing its particles, when compressed 

 by the superincumbent column, from regaining their ori- 

 ginal condition, when the pressure is removed." 



Remarks. — In making experiments upon the density of 

 sea water, Scoresby's Marine Diver is the only instrument 

 calculated to procure it with certainty, from any given 

 depth. For the mechanical compression of water, the Ba- 

 thometer of our countryman Perkins should be used. " In 

 this machine, water, inclosed in a brass tube, the sides of 

 which need not exceed one tenth of an inch in thickness, 

 is compressed by a solid piston, sliding in a leathern collar, 

 and acted on by the superincumbent column when sunk in 

 the depths of the ocean." (Brand's Journal, and this Jour- 

 nal V. III. p. 347. 



Depth. — It is supposed by Hydrographers, and with ap- 

 parent probability, that the inequalities of the bottom of 

 the ocean are equal to those on the surface of the land. 

 From 1774 to 1785, Cook was endeavouring to find sound- 

 ings in the Pacific with 250 fathoms of line. Scoresby has 

 used 1200 fathoms in the arctic seas, without finding bot- 

 tom. 



Near to land the depth varies according to the elevation 

 of the coast — if this be steep, the water is usually deep, and 

 the anchorage bad. 



Remark. — The sounding line generally used, is inaccu- 

 rate. The best machine for this purpose, is one invented 

 by Massy, now constantly used in the English Navy, with 



