OB01 "'.v. 



GEOLOGY. 



B3J 



niped*. before the lubiUnce of olhen was laid on the bed of the 

 M*. Sine* life was developed on the globe, if geology has rightly 

 interpreted the monuments of nature, there has never been any con- 

 siderable period during which the land or ca via wholly deprived of 

 organic beings; but as the condition of the globe changed, <li form* 

 of life were altered, old race* perishod.new creations were kWaktoad, 

 the mim of auiinal and vegetable existence wan continually augmented, 

 and the variety of their forms ami habits continually multiplied, as 

 the conditions of land and sea were diversified, until man was added 

 to the wonders of creation, and historic time began. 



If then, through all past geological time, organic life has changed 

 iU aspect as physical conditions varied if the present physical 

 aspect of the globe is derived from previous physical revolutions, 

 must we look on the present system of organic being, adapted to the 

 present physical conditions, as similarly derived by corresponding 

 revolutions from earlier systems of life, corresponding to earlier 

 Mutes of the land aud seat 



If the physical aspect of the globe ia now changing, does its orgapic 

 enrichment "vary likewise; or ia the relation of organic life and 

 physical condition oiic of coincidence merely one of those adjust- 

 ment* independent in its nature, though associated iu time and 

 Ritu.ition, which offer the most convincing proof of continual super- 

 intendence of the divine lawgiver of nature ? 



Though we cannot here enter at Urge on a subject which requires 

 tin' dcUkils which are found under another head [Onc.tMC UKMAINS], 

 there nre poinU of too general importance, in reasoning on the present 

 condition of the globe, to be wholly omitted : 1. Th relation of 

 furm and structure between the living and extinct worlds of life ; 

 2. The distribution of the existing forms of life, in reference to the 

 geographical features and geological history of different parts of the 

 globe. 



The relation of living to extinct races of planU and animals is 

 various. In number, the Recent Flora is perhaps 100 times as con- 

 M.lerablc as the Fossil Flora, aud though this is in Borne degree owing 

 to the circumstance that, land-plants, insects, Ac., must necessarily be 

 comparatively rare in marine strata, yet the vast number of individual 

 plants accumulated in coal tracts does not appear to justify a very 

 nigh estimate of the variety of specific forms of plants in early 

 periods. The same is true of the marine races of shells, Crnttacea, 

 fishes, Ac. ; fur both the total number of species, and the relative 

 number .to a given thickness of strata, augment from the early towards 

 the later formations, and are greatest of all iu the tertiary strata, 

 which in character of organic life most nearly resemble the modern 

 productions of nature. 



On comparing the living with the vanished tribes of plants and 

 nnimals, we are struck with the fact that hardly one species of the 

 fossil kingdom is so peculiar iu its structure that nothing at all like 

 it is now in existence. Recent analogies of extinct forms are con- 

 tii.ually and unexpectedly presented to u.i by the attentive voyagers 

 who now explore the moat remote and unknown regions of the land 

 and sea, and continually revealed to us by the discoveries of compa- 

 rative anatomy, which detects in common forms traces of analogies to 

 extinct creations formerly altogether unsuspected. Thus the belem- 

 nite, the trilobitc, the ichthyosaurus, are reduced to their proper 

 i among ifoUiuca, Crustacea, and jRrptilia, and the whole 

 extinct and living world of nature becomes united into one general 

 system. 



I'.ut this indubitable affinity between the plants and animals now 

 living and those which adorned the world in earlier ages does not 

 require us to adopt the speculations of Linuaras, Oken, Lamarck, St. 

 Ililnire, and the anonymous author of the 'Vestiges of the Natural 

 History of Creation,' that specific forms of plants and animals ore no 

 further permanent than the circumstances which surround them; 

 that as these change those vary ; that the immense variety of organic 

 utriicturo may have been denved from a few primitive types the 

 living gavial from the fossil Ttlrotauru*, the living cuttle from the 

 (n'fil /IflrmHatfjiia, the living from the fossil Kijuiscta. This doctrine, 

 plausible as it seems, and flattering as it is to that propensity in man 

 to derive everything from a beginning of which his own lenses may 

 give some notion, must be rejected for three reasons : 



1. In existing plants and animals the experience of mankind, for 

 2000 or 3000 years, has shown no essential change. 



2. There is no proof, drawn from examination of fossil reliquiro, 

 of this axsnmed change from one species to another, much less from 

 one genus to another. On the contrary, it is a very striking truth, 

 illustrated in almost every group of fossils, that while the same specie* 

 retains through many deposits of different age its essential charac- 

 teristics, new ones come into view in many of these strata, not by a 

 gr.idnal change, but by a sudden development. 



3. The destruction of old race* and the introduction of new 

 appear in many cases to have been sudden and complete, at least 

 fatally. 



In considering the distribution of existing forms of life, with 

 reference to the geographical features and geological history of 

 different parts of the globe, we cannot avoid being struck with the 

 fact that each species, each genus, and often each family, of plant* 

 mid animals, is especially abundant in and often exclusively confined 

 to particular ports of the land or sen, even among those animals 



whose powers of locomotion are the greatest. Among fishes, birds, 

 and swift quadrupeds, this attachment to locality is scarcely lea* 

 remarkable than among Plant*, Zoophytes, and Moltutca, which have 

 no means of diffusing their races, except what winds ami current* 

 give. It has therefore become an admitted truth in the philosophy 

 of natural history, that there are certain regions of the land and 

 tract* of the sea for which particular groups of plants and animals 

 were specially created, and to which for the most part their existence 

 is still confined. 



The living species of plants and animal* which most nearly resemble 

 fossil races are variously distributed over the globe. Tree-ferns, 

 gigantic Kquiictatttr, and other plant* illustrative of the Flora of the 

 carboniferous period, may be found in Brazil, the Indian Islands, and 

 Australia; coniferous plants occur in colder latitudes, or at gi 

 heights in the tropics, as well as in the lias; Cyeadaetft occur in 

 South Africa and Australia, and tropical America, as well as in the 

 oolites. The recent Trigonia and Cerithium giyanteum ore found mi 

 she Australian shore ; J'huladomya was washed on the island of 

 Tortuga : and CacMtta belongs to the Indian Ocean. Linynl-i IK 

 Tound in the Moluccas ; but Tertlratuta in all seas : the nearest 

 living form to the old fossil crocodiles inhabit* the Ganges; while 

 tho bony pike, whose scales resemble those of Mtgalichthy*, li . 

 Lake Ontario. 



Geological Time. There is perhaps no more difficult problem in 

 geology than the determination of the length of time which has 

 elapsed during the formation of the whole or any definite ]> 

 the crust of the earth. Time, as measured by generations of m< -n, 

 fails to carry us bock to remote geological epochs ; man is but a 

 recent visitor of the globe; compared even to the secondary strata 

 Ilia date is of yesterday, for all the existing forms of life cease with 

 the lower tertiary rocks, only small proportions of them occur in tho 

 middle of that series, and traces of men have nowhere been sivn in 

 any but the most modern parts of the stratified masses of the globe. 

 If then the history of the human race does not commence till after 

 the deposition of at least the greater part of the tertiary strata, 

 liy what rules shall we attempt to compare the few thousand 

 years of his existence with the earlier periods of the history of tho 



In a vague sense, nothing appears more obvious than the couch, ; >n 

 universally admitted among geologists, that the earth is of vast 

 antiquity, yet nothing more eludes the grasp of reasoning than the 

 seemingly easy task of computing its age. The rocks are indeed full 

 of monuments of time, " rudera longinqui senslm pncterlapsi :rvi," 

 but we have not yet learned fully to decipher them. 



When we behold thousands of strata piled on one another iu a 

 regular series, each distinct by some peculiarity from the others ; 

 when we find among these the original products of chemical action 

 (as limestone), the slow sediments from gentle motion (clays), rough 

 .-;md and pebbles implying greater agitation ; how can we refuse to 

 admit that Ion? time elapsed during the often repeated ch 

 chemical and mechanical agencies of water over the same portions of 

 the bed of the sea ? 



When among these strata we observe the remains of plants and 

 animals, various in their kinds, regular in their distribution, so as to 

 prove that at successive times the same part of the sea nourished 

 successive races of animals, and buried iu its sediment distinct races 

 of plants, where in modern nature is it conceivable that such rcpe- 

 titions of change, in all the ranks of creation, could take place except 

 by the aid of almost immeasurable time ? 



Descending to minuter inquiries, we find some particular strata 

 composed of fragments derived from a more ancient rock, which 

 after being deposited in water, was indurated, raised to the surface, 

 wasted by drainage, and again collected in rolled fragments on the 

 bed of another sea. The trees which are imbedded in certain rocks 

 (coal-measures, lias, Portland oolite, &c.), are often known by their 

 rings of growth to be some decads of years old, and iu particular 

 cases (Dirt-bed of the Isle of Portland) it is supposed that their 

 whole existence passed between the formation of two bed* ,,i 

 stone. 



Every country affords examples of certain fossil shells confined to 

 oven a thin layer of shale, sandstone, limestone, or ironstone, and in 

 some instances (near Leeds and Bradford) tho youngest embryo 

 lloniatila and the oldest full-grown shell are found in one 1 

 6 or 1 2 inches thickness, in that alone, and apparently in the place of 

 their i|iiift existence, so as to indicate that the lifetime of Hint 

 (ioniiititc (0. Litleri) was consumed during the accretion of one 

 calcareous )>.<!, wl.i. h is about j,,V, D th part of tho thickness of the 

 coal-measures whose history it curicl^e'. 



If again, among those strata produced by watery action wo find 

 alternations of volcanic rocks, and learn that at particular cpoclm in 

 the series of deposits mountains were raised from the sea, land 

 clothed with forests was submerged, and the physical geography of 

 particular regions entirely changed, we see clearly that such repeated 

 revolutions of nature agree with the history of the organic creations 

 in refuting the narrow views of those who would limit the age of 

 the world to the short annals of mankind. 



But how are we to proceed further, so as to clothe with a more 

 philosophical character these almost poetic notions of the immensity 



