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temperature, at small depths, does not 

 coincide with the mean temperature of 

 the atmosphere above it. 5. Igneous 

 matter has been ejected at all periods 

 from the interior of the earth. 6. Active 

 volcanoes occur widely spread over the 

 surface of the world, and so closely re- 

 semble each other, that they may be con- 

 sidered as produced by a common cause, 

 and that cause deep-seated. 7. Geologi- 

 cal phenomena attest a great decrease of 

 temperature on the surface of the globe. 

 8. A decreased temperature of the earth 

 would, by radiation, produce the various 

 mountain ranges and fractured strata found 

 on the surface of our planet. " When all 

 these circumstances," says the able and 

 learned author, H. T. De la Beche, Esq., 

 from whose work, Researches on Theo- 

 retical Geology, I have extracted the pre- 

 ceding observations, " are taken into con- 

 sideration, and we add the probability 

 that heat counteracts the effects of gravity 

 in the sun and certain planets, and that 

 the free passage of the particles of terres- 

 trial matter among each other was neces- 

 sary to produce the figure of the earth, the 

 evidence in favour not only of a central 

 heat at present, but also of a heat of far 

 greater intensity at remote geological 

 epochs, becomes exceedingly strong ; so 

 strong, indeed, that there is some diffi- 

 culty in resisting the impression that we 

 have, by various means, made as fair an 

 approximation to the truth, as the nature 

 of the subject will admit. If the theory 

 of central heat be founded on probability, 

 the very general occurrence of tilted and 

 fractured rocks is of easy explanation." 



M. Adolphe Brongniart has shewn, 

 says Professor Buckland, "that the exist- 

 ing submarine vegetation seems to admit 

 of three great divisions which charac- 

 terize, to a certain degree, the plants of 

 the frigid, temperate, and torrid zones. 

 If we take a general review of the remains 

 of terrestrial vegetables, that are distri- 

 buted through the three great periods of 

 geological history, we find a similar di- 

 vision of them into groups, each re- 

 spectively indicating the same successive 

 diminutions of temperature upon the land, 

 which have been inferred from the re- 

 mains of submarine vegetation. Thus, 

 in strata of the transition series, we have 

 an association of a few existing families of 

 endogenous plants, chiefly ferns and equi- 

 setacese, with extinct families both endo- 

 genous and exogenous, which some mo- 

 dern botanists have considered to indicate 

 a climate hotter than that of the tropics 

 of the present day. In the secondary 

 formations, the species of these most 

 early families become less numerous, and 

 many genera and families entirely cease; 



while a large increase takes place in 

 Cycadese and Coniferse, two families com- 

 prehending many existing forms of vege- 

 tables. The united character of the 

 groups thus associated, indicate a climate, 

 whose temperature was nearly similar to 

 that which prevails within the present 

 tropics. In the tertiary deposites, the 

 greater number of the families of the first 

 series, and many of those of the second 

 disappear, and a more complicated dicoty- 

 ledonous vegetation takes place of the 

 simpler forms, and the general character 

 marks a climate nearly approaching to 

 that of the Mediterranean. This third 

 great change in the vegetable kingdom is 

 considered to supply another argument in 

 favour of the opinion, that the temper- 

 ature of the atmosphere has gone on con- 

 tinually diminishing from the first com- 

 mencement of life upon our globe." 



" To know the temperature of the in- 

 terior parts of the globe at the present 

 period," says Professor Phillips, " and the 

 effects depending on its condition in this 

 respect, is important, as furnishing one, 

 and that, perhaps, the most instructive, 

 of the elements for computing the changes 

 which have, in earlier times, affected its 

 structure and configuration, and varied 

 its adaptations for organic life. That 

 the earth has below its surface a source 

 of great heat, independent of solar in- 

 fluence, is perfectly ascertained by vol- 

 canic phenomena ; that this heat is very 

 generally diffused, is equally certain, from 

 the extent of country in which thermal 

 springs are found ; that it is universally 

 spread below our feet, becomes conti- 

 nually more and more probable from ex- 

 perimental researches." 



From a series of experiments, it ap- 

 pears that the temperature of the earth's 

 crust increases at the rate of 1 Fahren- 

 heit for every forty-five feet of perpendi- 

 cular descent. 



The uninjured corals and chambered 

 univalves of Iglulic, Melville Island, and 

 other high latitudes, sufficiently prove 

 that during the carboniferous period 

 there was an elevated temperature even 

 in the northern regions bordering on the 

 Arctic circle. The heat and the humidity of 

 the air, and the uniformity of climate, ap- 

 pear to have been most remarkable when 

 the oldest strata hitherto discovered were 

 formed. The approximation to a climate 

 similar to that now enjoyed in these la- 

 titudes does not commence till the era of 

 the formations termed tertiary ; and while 

 the different tertiary rocks were depo- 

 sited in succession, the temperature seems 

 to have been still further lowered, and to 

 have continued to diminish gradually, 

 even after the appearance upon the earth 



