20 ; PILYSICAL GEOGRAPHY OF THE SEA. 
alone must have extended over several square miles. ‘The 
colour of the water was like that of a river which has flowed 
through a red clay district, and a strictly defined lme separated 
the red stream from the blue water.” 
In the neighbourhood of Callao, the Pacifie has an olive-green 
colour, owing to a greenish matter which is also found at the 
bottom of the sea, in a depth of 800 feet. In its natural state 
it has no smell, but when cast on the fire, it emits the odour of 
burnt animal substances. 
Near Cape Palmas, on the coast of Guinea, Captain Tuckey’s 
ship seemed to sail through milk, a phenomenon which was 
owing to an immense number of little white animals swimming on 
the surface, and concealing the natural tint of the water. 
The peculiar colouring of the Red Sea, from which it has 
derived its name, is owing to the presence of a microseopic alga, 
sui generis, floating at the surface of the sea and even less 
remarkable for its beautiful red colour than for its prodigious 
fecundity. 
I could add many more examples, where, either from minute 
algz or from small animals, the deep blue sea suddenly appeared 
in stripes of white, yellow, green, brown, orange or red. For 
fear, however, of tiring the reader’s patience, I shall merely 
mention the olive green water, which covers a considerable part 
of the Greenland seas. It is found between 74° and 80° N. lat., 
but its position varies with the currents, often forming isolated 
stripes, and sometimes spreading over two or three degrees of 
latitude. Small yellowish Meduse, of from one-thirtieth to one- 
twentieth of an inch in diameter are the principal agents that 
change the pure ultramarine of the Arctic Ocean into a muddy 
green. According to Scoresby, they are about one-fourth of 
an inch asunder, and in this proportion a cubic inch of 
water must contain 64, a cubic foot 110,592, a cubic fathom 
23,887,872, and a cubic mile nearly twenty-four thousand 
billions! From soundings made in the situation where these 
animals were found, the sea is probably more than a mile deep; 
but whether these substances occupy the whole depth is un- 
certain. Provided, however, the depth to which they extend 
be about 250 fathoms, the immense number of one species 
mentioned above may occur in a space of two miles square; 
and what a stupendous idea must we form of the infinitude of 
