THE TERTIARY SYSTEM. 749 



cumbrous and inconvenient ; but such a structure would be no disadvantage to a crea- 

 ture destined to live principally in fresh-water lakes and rivers like the hippopotamus. 

 It is conceived, therefore, to have been an aquatic, employing its tusks for the purpose of 

 tearing up the roots of vegetables at the bottom of the water, which, as the teeth show, 

 constituted its food. They may also have served for defence, and likewise to assist in 

 dragging the huge body of the animal out of the water as occasion required, by being 

 hooked on the bank a purpose to which the walrus applies the same implements. 



The remains of organic existence, found in the median and other tertiaries, conduct us 

 from the colossal and imposing to the minute and microscopic ; for beds occur entirely 

 composed of the fossil relics of animalculites those infinitesimal forms now present in 

 our lakes, rivers, and streams, invisible to the unassisted sight, whose perfect organisation 

 places them among the wonders of the creation. They were formerly supposed to be little 

 more than mere particles of matter endowed with vitality ; but Ehrenberg has discovered 

 in them an apparatus of muscles, intestines, teeth, different kinds of glands, eyes, nerves, 

 and organs of reproduction. Yet some of the smallest are not more than the 24,000th of 

 an inch in diameter, the thickness of the skin of their stomachs not more than the 

 50,000,000th part of an inch, a single drop of water having been estimated sometimes 

 actually to contain 500,000,000 individuals. Not less astonishing is their power of mul- 

 tiplication, an individual of one species increasing in ten days to 1,000,000, on the 

 eleventh day to 4,000,000, and on the twelfth day to 16,000,000 ; while, of another kind, 

 Ehrenberg states that one individual is capable of becoming, in four days, 170,000,000,000 ! 

 To this distinguished naturalist we are indebted for the development of the fact, that ages 

 ago our world was rife with these minute organisms, belonging to a great number of 

 species, whose mineralised skeletons actually constitute nearly the whole mass of some 

 tertiary soils and rocks several feet in thickness, and extending over areas of many acres. 

 Such is the Polirschiefer, or polishing slate of Bilin in Bohemia, which occupies a surface 

 of great extent, probably the site of an ancient lake, and forms slaty strata of fourteen 

 feet in thickness, almost wholly composed of the silicified shields of animalcules. The 

 size of a single one, forming the polishing slate, " amounts upon an average, and in the 

 greatest part, to ^-1^- of a line, which equals ^ of the thickness of a human hair, reckon- 

 ing its average size at ^ of a line. The globule of the human blood, considered at ^J^, 

 is not much smaller. The blood globules of a frog are twice as large as one of these 

 animalcules. As the Polirschiefer of Bilin is slaty, but without cavities, these animal- 

 cules lie closely compressed. In round numbers, about 23 millions would make up a 

 cubic line, and would in fact be contained in it. There are 1728 cubic lines in a cubic 

 inch; and therefore a cubic inch would contain, on an average, about 41,000 millions of 

 these animals. On weighing a cubic inch of this mass, I found it to be about 220 grains. 

 Of the 41,000 millions of animals, 187 millions go to a grain; or the siliceous shield of 

 each animalcule weighs about -^j- millionth part of a grain." Such is the statement of 

 Ehrenberg, which naturally suggests the reflection of the French philosopher, that if the 

 Almighty is great in great things, he is still more so in those which are minute ; and 

 furnishes additional data for the well-known moral argument of the theologian, derived 

 from a comparison of the telescope and the microscope : " The one led me to see a 

 system in every star ; the other leads me to see a world in every atom. The one taught 

 me that this mighty globe, with the whole burden of its people and of its countries, is but 

 a grain of sand on the high field of immensity. The other teaches me, that every grain 

 of sand may harbour within it the tribes and the families of a busy population. The one 

 told me of the insignificance of the world I tread upon. The other redeems it from all 

 insignificance ; for it tells me that in the leaves of every forest, and in the flowers of 

 every garden, and in the waters of every rivulet, there are worlds teeming with life, and 



