Mr Livingstone on the Thermal Springs of Yom-Mach, 161 
rarely so low as 45°. The mountains here, and I have been in- 
formed, in such parts of China as Europeans have visited, are 
covered to the tops with a hard crust of red earth, commonly 
called Tilt. This is often converted into terraces, on which 
most vegetable productions seem to thrive, and is that most pro- 
per for the cultivation of the tea-plant, but it screens from our 
view the structure of nearly all the mountains, which must 
long retard our acquaintance with the geology of China. 
The amphitheatre which surrounds the hot-wells, inay be 
imagined by some to^e the remains of a volcanic crater on a 
large scale, which now retains scarcely sufficient heat to make 
water boil, but the want of every vestige of volcanic produc- 
tions seems to be an insuperable objection to this supposition. 
The electric hypothesis advanced by several naturalists, and 
which has been acutely illustrated by Mr P. Inglis, seems to 
afford an interesting explanation of our thermal springs. Such 
stratification as his theory requires, may doubtless exist here ; 
and the sea-water may serve to excite an immense natural gal- 
vanic pile, one of the poles of which may terminate where the 
hot-springs on Yom-Mack have tlieir origin, 
Macao, 1 
\9>th April 1821. f 
Art. XXVIII. — Remarhs on the Specific Gravity (f Sea-Water 
in dfil^ere7it Latitudes., and cm the Temperature qf the Ocean 
at different Depths By Dr J. C. Horner. 
The observations on the specific gravity of the sea- water 
have been already drawn up in an instructive table by the 
* Having already laid before our readers the Observations on the Specific Gra- 
vity of the Sea-Water, and on the Temperature of the Sea made during the three late 
Expeditions to the Arctic Regions, under Captain Ross, Captain Buchan, and Captain 
Parry, and also the observations of Captain Scoresby, Mr Livingstone, Dr Marcet, 
and Dr Traill on the same subject, we are now enabled to extend tbe series by those 
which have been made during Kotzebue’s Voyage of Discovery. M. Horner, th^e 
author of^the “ Rennarks,” was, we believe. Astronomer to the Russian Voyage of 
VOL. VI. NO. 11, JANUARY 1822. L 
