THE DRIFT OF THE SEA, 
255 
biiigs of the sea-heart, which take place in consequence of the di- 
urnal changes in its temperature, call in the sunshine, the cloud 
without raiuj with day and nighty and their heating and radiating 
processes. And to make the case as strong as to be true to na- 
ture we may, let us again select one fifth of the Atlantic Ocean 
for the scene of operation. The day over it is clear, and the sun 
pours down his rays with their greatest intensity, and raises the 
temperature two degrees. At night the clouds interpose, and pre 
vent radiation from this fifth, whereas the remaining four fifths, 
which are supposed to have been screened by clouds, so as to cut 
off the heat from the sun during the day, are now looking up to the 
stars in a cloudless sky, and serve to lower the temperature of the 
surface waters, by radiation, two degrees. Here, then, is a differ- 
ence of four degrees, which we will suppose extends only ten feet 
below the surface. The total and absolute change made in such 
a mass of sea water by altering its temperature four degrees is 
equivalent to a change in its volume of three hundred and ninety 
thousand millions of cubic feet. 
552. Do not the clouds, night and day, now present themselves 
to us in a new light ? They are cogs, and rachets, and wheels in 
that grand and exquisite machinery which governs the sea, and 
which, amid all the jarrings of the elements, preserves in harmo- 
ny the exquisite adaptations of the ocean. 
553. It seems to be a physical law, that cold-water fish are 
more edible than those of warm water. Bearing this fact in mind 
as we study Plate IX,, we see at a glance the places which are 
most favored with good fish-markets. Both shores of North 
America, the east coast of China, with the west coasts of Europe 
and South America, are all washed by cold waters, and therefore 
we may infer that their markets abound with the most excellent 
fish. The fisheries of Newfoundland and New England., over 
which nations have wrangled for centuries, are in the cold water 
from Davis's Strait. The fisheries of Japan and Eastern China, 
which almost, if not quite, rival these, are situated also in the eold 
water. 
Neither India, nor the east coasts of Africa and South America, 
where the warm waters are, are celebrated for their fish. 
554. Three thousand American vessels, it is said, are engaged 
in the fisheries. If to these we add the Dutch, French, and En- 
