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REFRIGERATION OP THE GLOBE. 



REFRIGERATION' OF THE GLOBE. 



*> 



and stellar spaces around u. But though such a deduction of pheno- 

 mena from a primal condition of our planet is or appears to be 

 correct enough to justify geologists in employing the hypothesis as a 

 means of discovering truth, they must be careful neither to disregard 

 inquiries into the certainty of the fundamental assumption, nor to 

 neglect a scrupulous examination of its consequences. 



On the first point Professor Whewell communicated to the Geo- 

 logical Section of the British Association at Dublin (1835), some 

 observations which are likely to be influential on the second point, and 

 which can neither be condensed nor amended. 



" The heat of the interior parts of the earth has always been treated 

 of by those who have established the theory of heat upon mathematical 

 principles. They have hitherto considered it aa proved upon such 

 principles, that the increase of temperature of the substance of the 

 earth as we descend proves the reality of an original hent. But M. 

 Poi.son, in his ' The'orie de la Chaleur," just published, dissents from 

 this opinion, and is disposed to assign another reason for the higher 

 temperature below the surface. He observes that the cosmical regions 

 in which the solar system moves have a proper temperature of their 

 own ; that this temperature may be different in different parts of the 

 universe ; and that, if this be so, the earth would be some time in 

 acquiring the temperature of the part of space in which it has arrived. 

 This temperature will be propagated generally from the surface to the 

 interior parts. And hence, if the solar system moves out of a hotter 

 into a colder region of space, the part of the earth below the surface 

 will exhibit traces of that higher temperature which it bad before 

 acquired. And this would by no means imply that the increase of 

 temperature goes on all the way to the centre." (' Report of the 

 Association for 1835,' p. tii5.) 



A speculation, perhaps in reality involving such views as those of 

 nson, though founded on examinations and inferences among the 

 Helvetic Alps, was subsequently brought prominently before the 

 geological world by H. Agataiz. According to this very distinguished 

 -list, there is evidence from the peculiar effects left by glaciers, 

 in the valleyi of Switzerland and on the surface of the Jura Mountains, 

 that the icy mantle which now wraps the High Alps once filled the 

 valleys for miles beyond its present limits, and, consequently, that the 

 block* of Mont Blanc and the Valorsine were carried across the Lake 

 of Geneva to the Jura, by a mere glacier movement across an ice-filled 

 hollow. Dr. Buckland and Mr. Lyell have endeavoured by similar 

 evidence and reasoning, by the evidence of scratched, smoothed and 

 grooved surfaces of rock, and the appearance of moraine heaps in the 

 Highlands of Scotland, near Edinburgh, and in Cumberland and 

 Westmoreland, to prove that glaciers anciently covered Urge tracts of 

 the Caledonian and Cumbrian regions. (' GeoL Proceedings,' 1840, 

 Xovembrr and December.) 



Moreover, it is understood to be the opinion of H. Agassis that the 

 icy covering thus attempted to be demonstrated by its remaining 

 effects in the mountainous parts of Great Britain, " once extended over 

 all the north of Europe and the north of Asia and America," and that 

 in th " mats of ice the elephants and other mammalia found in the 

 {men mud and gravel of the arctic regions were imbedded at the time 

 of their destruction." To the quick melting of this immense man of 

 ice and the currents of water which resulted, the author attributes the 

 transport and deposition of the " masses of irregularly rounded 

 boulders and gravel which fill the bottom of the valleys, innumerable 

 boulders having at the same time been transported, together with 

 mud and gravel, upon the masses of the glaciers then set afloat " (See 

 the work of M. Agasuz, entitled ' Etudes stir les Glaciers de la Suisae,' 

 and the accounts of his observations before the British Association at 

 Glasgow in 1840.) 



Now it is obvious that in examining this speculation, two ways are 

 open : first, a careful eomjarison of the phenomena with the hypo- 

 thesis which is proposed for their explanation; secondly, an inquiry 

 into the probability of the conditions which might render such a 

 general and extreme refrigeration of the globe as the hypothesis 

 requires pauible. Confining our remarks to the former process, we 

 may observe : first, that to admit the ancient existence of glaciers in 

 some of the Highlands and Cumberland valleys which display ijlanal 

 efectt, is one thing ; to admit </i an the physical cause of th 



dispersion of boulders and gravel, another. GLwiers are found at this 

 day in corresponding latitudes and at corresponding elevations in the 

 southern parts of America : a local effect of causes which may be con- 

 ceived to have formerly produced an equal effect in the northern zone : 

 but the distribution of the boulders and gravel is so peculiar and yet 

 so various, the dispersion of them so wide in regions where, according 

 to the present configuration of the land, they could not be pushed by 

 glaciers, nor carried by floating ice; and the connection of these 

 circumstances with a great change of organic life, so strict, that it is 

 hardly conceivable such effects could be due to anything but a cause 

 simultaneously general or successively repeated. Of the physical 

 causes by which the explanation of this great phenomenon has been 

 attempted, it will suftce to mention three : 



1 . Great and extensive oceanic action consequent on mighty mis- 

 placement* of the rolid land, and corresponding changes of land and 



1 Repeated local displacement* of land and sea, and consequent 

 literal action. 



3. The melting of great circumpolar glaciers, and the drifting of 

 floating ice. 



During the period of nearly twenty years which has elapsed since 

 the first publication of the preceding portion of this article, much has 

 been done on the subject, both by mathematicians and geologists. The 

 consequences of admitting the hypothesis of the refrigeration of the 

 globe, and the history of the gravel containing sea-shells alluded to 

 above, and now called the "northern drift," have been rigorously 

 investigated. Until within this period, the only change of climate 

 which had been recognised by geologists as having taken place during 

 the earth's geological history was one from a higher to a lower tempe- 

 rature ; and for those who believed in the primitive heat of the globe, 

 however originated, that heat afforded one obvious cause for this 

 higher temperature at remote geological epochs. When, however, an 

 examination of the phenomena of the " glaeul epoch " (first conceived by 

 Agassiz) during and on the gradual termination of which that drift was 

 accumulated, rendered it necessary to recognise a change of climate in 

 our own region of the globe (as iudicated by the facts noticed in the 

 proposition 1 above) from a lower temperature during that period to a 

 hU'her subsequent temperature, new conditions were added to the 

 problem. As we have seen, two other causes had been already sug- 

 gested, which might possibly account not only for a change from a 

 higher to a lower superficial temperature, but also for oscillatory 

 changes. One of these assigned causes rested on the fact of the trans- 

 latory motion of the whole solar system in space, and the hypothesis 

 proposed by Poisson of the variable temperature of the different 

 regions through which it might pass ; thus the other cause assigned, 

 pointed to in propositions I and '2 above, was the influence of different 

 configurations of land and sea on the climatal state of particular 

 portions of the earth s surface. No attempt, however, was made to 

 examine the efficiency of these different causes to account for all the 

 phenomena which might be referable to them, until Mr. William 

 Hopkins, F.R.S., of St. Peter's College, Cambridge, when president of 

 the Geological Society of London, undertook a remarkable investigation 

 contained in a paper communicated to that society iu 1651, and pub- 

 lished in its ' Quarterly Journal,' vol viii., pp. 56 92, ' On the Causes 

 which may have produced Changes in the Karth's Superficial Tempe- 

 rature.' He also returned to the subject in his anniversary address to 

 the society in the following year, printed in the same volume. From 

 these papers is derived the following view of what may be regarded as 

 the actual condition of the theory of the refrigeration of the globe ; 

 but we have stated the subject in a somewhat different order from that 

 adopted by the author. 



If there be any propositions in experimental science which may be 

 deemed incontrovertible, the following, Mr. Hopkins conceives, is one 

 of them : " If a mass of matter such, for instance, as the earth with 

 its water and its atmosphere be placed iu space of which the tempe- 

 rature is lower than its own, it will necessarily lose a portion of its 

 heat by radiation, until its temperature ultimately approximates to 

 that of the circumambient space, unless this reduction of temperature 

 be prevented by the continued generation of heat." This proposition, 

 it will be seen, is equivalent to an explicit statement of the theory of 

 the refrigeration of the globe in all its generality. Now, assuming the 

 primitive temjwrature of the globe to have been very much greater 

 than at present, there is manifestly no difficulty in accounting for any 

 higher superficial temperature than the present, at past epochs, pro- 

 vided those epochs be sufficiently remote. Tuey must, however, be 

 exceedingly remote to enable us thus to account for a variation of 

 temperature which should sensibly atl'ect the climatul conditions in 

 any part of the earth. If the cooling of the earth were to continue 

 for an indefinite period of time, assuming the temperature of external 

 space, the sun, and the earth's atmosphere to remain as at present, 

 the superficial temperature would approximate indefinitely near to a 

 certain limit. The diilerenoe between that limit and the earth's 

 present superficial temperature is the eil'ect due t j the remains of the 

 primitive heat. Theory gives us a simpb relation between the amount 

 nf this ett'ect and the rate of increase of temperature in descending 

 beneath the earth's surface. Knowing the one, we cau immediately 

 determine the other, and thus, having ascert lined the rate of increase, 

 we know the amount of superficial temperature which U now due to 

 the earth's primeval heat, assuming always that he.it to be the cause 

 of the existing internal temperat ire of the globe. This amount is 

 thus proved not to exceed about the one-thirtieth part of a degree of 

 the Centigrade thermometer, so nearly has the earth's supeifiuiul tem- 

 perature approximated to that ultimate limit beyond which it could 

 never descend, supposing external conditions to remain the same. It 

 has been shown, on high mathematical authority, that to reduce the 

 superficial temperature of the earth by one-half of the above amount, 

 or one-sixtieth of a centesimal degree, it would require the enormous 

 period of one hundred th-auand milLitaa of yenn. " It would doubt- 

 less," says Mr. Hopkins, " require us to go back into the p:ist some 

 such immense period as this to arrive at the epoch when the super- 

 ficial temperature should have exoeedeJ its present amount by even 

 one or two degrees. At the same time, the rate of increase of tempe- 

 rature in descending beneath tne surface would be much more rapid 

 than at present. [The present rate is about 1 Fahr., or J C. for every 

 BO feet of depth.] If the superficial temperature amounted to ~i C. 

 above its ultimate limit, instead of having jfcth of a degree, the rate at 



