14G 



EECEEATIVE SCIENCE. 



have inscribed their records on the stony 

 cliff-walls of the gorge through which their 

 eddying waters foam onwards to the sea. 

 How many ages older than that wonderful 

 cataract those alluvial gravels are no mau 

 can teU; but older, indeed, they must be, 

 referring as they do to former geological and 

 physical changes and conditions of the land. 

 And yet, whUe on a vertical scale of the 

 rock-strata, where an inch would represent 

 a thousand feet, the whole era of the full 

 deposit of those alluvial beds, in all their 

 thickness, would not be equal to a pen-line, 

 the level of these first-known traces of 

 marine Poraminifers would be some six or 

 S3ven feet down. 



During all those vast intermediate ages, 

 such tiny living things have swarmed in 

 ocean, lake, and river, in earth and air. "We 

 cannot break down any friable freestone, 

 such as oolite or Bathstone, any sandstone, 

 limestone, or clay, without finding abundant 

 specimens of ancient Microzoa in the dried 

 and sifted dust. In those rocks, too compact 

 to be reduced mechanically to powder with- 

 out crushing, such as the limestone from 

 Dudley, the marble from Matlock or West- 

 moreland, very thin polished sections will 

 reveal, under the magnifying power of the 

 microscope, some of their beautiful and pecu- 

 liar forms. Some rock -masses, indeed, such 

 as chalk and various tertiary marls, are wholly 

 composed of the perfect and well-preserved 

 shells and cases of ancient minute organisms. 



Amongst these microscopic fossils, how- 

 ever, are two classes, which beyond all others 

 have played, as they still continue to do, a 

 most important part in the accumulation of 

 massive sedimentary strata. Over how many 

 thousands of square miles in Europe alone 

 does the chalk, that in the lofty cliffs of 

 Dover ?ind of France presents us with a 

 thickness of a thousand feet, extend ? And 

 yet, in every cubic inch, a million perfect 

 individuals may be counted, besides the 

 broken shells and fragment- dust with which 



they are cemented together. So minute, 

 sometimes, are these rock-forming Microzoa, 

 that in the polishing slate of Bilin, for ex- 

 ample, forty-one thousand billions are esti- 

 mated within the same limit of a cubic inch. 

 In the former, the chalk, the organisms are, 

 however, much larger and marine ; still they 

 require a magnifying power of at least 250 

 linear, or 62,500 times, to render them intel- 

 ligibly, and a far higher power than this 

 for the examination of their intimate struc- 

 ture. In the latter, the Bilin slate, the 

 organisms are, for the most part, the silicious 

 lorica of vegetable diatoms, such as Mr. 

 Tuffen West has already described in a re- 

 cent state in his papers in this work. 



For the past seventy years, microscopic 

 objects, whether vegetable or animal, have, 

 for the most part, been commonly described 

 and spoken of as Infusoria, a name they first 

 derived from the almost universal presence of 

 animated atoms in water in which flower- 

 stalks had been steeped, and in other vege- 

 table infusions. The severer scientific scru- 

 tiny to which this, like every other depart- 

 ment of natural history has of late years 

 been subject, has shown that many very- 

 different classes, both of animals and vege- 

 tables, have been improperly included and 

 grouped under this now restricted title. 



Of the two classes of minute animals 

 which we have alluded to as principal con- 

 stituents of some rock-masses, neither is 

 infusorial. One of these, the Foraminifera, 

 belongs to the lowest grade of animal life — 

 the Protozoa, or globular animals ; the other, 

 the Entomostraca — however at first sight 

 it may seem to diverge from the familiar 

 crab or lobster type — belongs to the Crus- 

 tacea, or crust-sJielled animals, one of the 

 principal sub-divisions of the Articulate or 

 ring-formed group. Of each of these kinds 

 innumerable hosts are living at the present 

 hour, and they are as easily obtained in their 

 living as in their fossil state. 



It will be well, however, in this paper. 



