THE BASIN OF THE ATLANTIC. 
211 
chiefly made up of perfect little calcareous shells {Foraminifer(jB\ 
and contain, also, a small number of silicious shells {DiatomacecE). 
" It is not probable that these animals lived at the depths where 
these shells are found, but I rather thnik that they inhabit the wa- 
ters near the surface ; and when they die, their shells settle to the 
bottom. With reference to this point, I shall be very glad to ex- 
amine bottles of water from various depths which were brought 
home by the Dolphin, and any similar materials, either ' bottom,' 
or water from other localities. I shall study them carefully. . . . . 
The results already obtained are of very great interest, and have 
many important bearings on geology and zoology 
" I hope you will induce as many as possible to collect sound- 
ings with Brooke's lead, in all parts of the world, so that we can 
map out the animalculffi as you have the whales. Get your wha- 
lers also to collect mud from pancake ice, &c., in the Polar re- 
gions: this is always full of interesting microscopic forms." 
449. These little mites of shells seem to form but a slender 
clew indeed by which the chambers of the deep are to be thread- 
ed, and mysteries of the ocean revealed ; yet the results are sug- 
gestive ; in right hands and to right minds, they are guides to 
both light and knowledge. 
The first noticeable thing the microscope gives of the-se speci- 
mens is, that all of them are of the animal, not one of the mineral 
kingdom. 
450. The ocean teems with life, we know. Of the four ele- 
ments of the old philosophers — fire, earth, air, and water — perhaps 
the sea most of all abounds with living creatures. The space oc- 
cupied on the surface of our planet by the different families of 
animals and their remains is inversely as the size of the individ- 
ual. The smaller the animal, the greater the space occupied by 
his remains. Though not invariably the case, yet this rule, to 
a certain extent, is true, and will, therefore, answer our present 
purposes, which are simply those of illustration. Take the ele- 
phant and his remains, or a microscopic animal and his, and com- 
pare them. The contrast, as to space occupied, is as striking as 
that of the coral reef or island with the dimensions of the whale. 
The grave-yard that would hold the corallines is larger than the 
grave-yard that would hold the elephants. 
451. We notice another practical bearing in this group ofphys- 
