28 UNITY OF SYSTEM. 



Mammalia, appeared and flourished in the said succession, and the species 

 of each class having reached their perfection, or culminating point, dwindled 

 or were degraded, and generally completely exterminated previous to the 

 creation of smaller, fewer, and less highly-developed species of the same 

 class, which were the contemporaries of the kinds of the next higher class, 

 or higher forms of life, the latter being then for the first time distributed. 

 Nevertheless, each epoch, whose average duration amounts to millions of 

 years, is characterized by the presence of some creatures which are different 

 from all the others, and represent, though in a slight degree, the creatures 

 of the coming epoch. 



The whole of the earth had a warm climate during nearly all the period 

 from the epoch of Mollusca to that of Birds. Every one of the thousands 

 of species, and most of the genera of those ages have passed away, and 

 the details of this part of the earth's history are full of examples of the 

 law of degradation, and are all in accordance thereto. 



Of the revolutions of the earth, in which its system was disturbed or 

 convulsed, that which closed the Azoic age, or the period previous to the 

 existence of living creatures, was probably most nearly universal. 



The Radiata, Mollusca, Articulata, and Vertebrata appeared by some of 

 their kinds in very ancient times, and the first three almost or quite 

 together. The creatures of lower grade, such as Foraminifera, Medusae, 

 Confervae, and Fuci, whose office it is to reanimate, and to recall into 

 circulation more matter, are comparatively co-extensive with it, both as to 

 space and as to time, and supply abundant nourishment for the numerous 

 and voracious tribes of Mollusca, Crustacea, and Fishes. 



The epoch of Mollusca, or the Silurian Period, continued for a long 

 succession of ages, and with this class the Corals, the Crinoids, and the 

 Trilobites were associated. Then the Coral animalcules built the limestone 

 hills and mountains, and the Mollusca in size and organization far exceeded 

 those of the later creation, but their degradation, and finally their complete 

 cessation ensued. The last Trilobite lived in the seas of the carboniferous 

 epoch, and the last Ammonite existed in the Reptilian Age. In vegetation, 

 the epoch of sea-weeds only continued for a long time, and after its 

 diminution, that of flowerless trees, (Tree Equisetae and Tree Ferns,) and of 

 the Pine tribe succeeded, to be in its turn degraded before the appearance 

 of the present vegetation. 



* I must here take occasion to adopt the stereotyped notice of the newspapers, — "The 

 Editor does not hold himself responsible for the opinions of his correspondents;" and cer- 

 tainly, moreover, even after allowing, as I think may be allowed, a wide limit to the 

 term "day" of creation, as we are so expressly told that "One day is with the Lord as a 

 thousand years, and a thousand years as one day;" yet, I cannot conceive that any animals 

 can have lived on the earth while only yet in the act of being cooled from an "incandescent 

 state." — F. 0. Morris. 



