72 Dr. Fothergiil’s account of ice islands. 
surface must have come from a much colder region below. Ina hot, 
climate the surface of the sea was at 84°, while Capt. Ellis at the depth, 
of 3000 feet marked the temperature at 53° and at 5,346 feet of line 
out, he tells us, the temperature appeared the same, but there is rea- 
son to believe such a vast weight of line must have floated the lead in 
a horizontal direction and drawn him into a considerable error. For 
Lord Mulgrave at the depth of 4,680 feet found the thermometer. 
marked 26°, which is 6° below the freezing point of fresh water, and. 
even one below that of the sea water itself. 
By means of the marine bucket with valves accompanied with a. 
thermometer as proposed by Dr. Hales, sea water may be taken up 
at various depths and its temperature examined. That its ‘coldness 
depths s has been ascertained, and well known to nay- 
igators j in tropical seas in very. hot s€asons, where they draw it up for 
the purpose of making a cold bath, and for cooling their liquors. 
As the summits of lofty mountains, even in temperate climates, are 
constantly covered with snow, and the atmosphere itself at the altitude 
of less than four miles from the earth, although exposed to the direct 
rays. of the sun, is DEvereneens the region of perpetual frost ; and as na- 
ture pursuesa simplicity and uniformity in her operations, why may not. 
the Gotta of oS Soe so fear removed from the influence of the so- 
lar rays, be also, in certain latitudes, the seat of constant congelation ? 
But the art of sounding, indeed, is still very imperfect, and the myste- 
ries of the great deep remain to be explored by future researches. © 
Butit may be objected, that as the sea to a certain depth is warmer 
than shallows, it must be uniformly so to the bottom in consequence 
of the central heat of the earth ; otherwise whence proceed hot springs. 
and volcanos? To which it may be replied, experiments have already 
discovered very different temperatures at different depths, though the 
temperature of the earth in the Pera mines is 52°, and has never 
Cans po glee tein SPR aie a Ad el aking 
