Febbuary 1, 1896.] 



KNOWLEDGE 



35 



have profoundly altered the climate and left traces on the 

 tlora and faiina of the period. A similar remark applies 

 to the case of a maximum eccentricity and a summer 

 aphelion. The mean temperature would be little altered, 

 but the extremes would approach more closely to the mean. 

 Phenomena of this kind could be best investigated a little 

 to the south of the limit of glaciation ; and as we know the 

 date of the last period of maximum eccentricity, the identi- 

 fication of its results would be of use to geologists in all 

 problems relating to the age of the earth and its various 

 formations. 



Another theory, started by Prof. G. H. Darwin, seems 

 to me of great geological moment ; and here, again, if some 

 of the Professor's results are to be regarded as doubtful, it 

 seems certain that the tides must have been slowly diminish- 

 ing the velocity of the earth's rotation, and that in early 

 geological times the day must have been considerably shorter 

 than at present. The earth was therefore less heated in 

 the day time, and less cooled at night, and the extremes 

 of temperature which now exist must have been consider- 

 ably modified. As in the former case the mean temperature 

 would probably be unaltered, and the phenomena which 

 depend on it would be the same as at present ; but 

 delicate plants which would now be killed by a cold night 

 might have then flourished in this country. 



This is not all, however. The equatorial protuberance 

 of the earth is no doubt due to its rotation, and when the 

 rotation was more rapid the protuberance must have been 

 greater. How, then, was this equatorial protuberance 

 lessened '? As far as the ocean extends, the answer seems to 

 be clear — by a flow of water from the equatorial towards the 

 polar regions, and a consequent submergence of the land in 

 the temperate zones both north and south of the Equator. 

 The elevated land at the Equator would be slowly washed 

 away by rivers ; but if the earth's crust was thin, equilibrium 

 might be more speedily restored by volcanic outbursts beyond 

 the limits of the tropics. Lava might stream out until the 

 laud at the Equator was sufficiently lowered and that in the 

 neighbourhood of the outbursts raised by the operation. 

 Such volcanic outbiusts might mask the simultaneous 

 rising of the sea-level in the same localities. These polar 

 ocean-currents would, in the northern hemisphere, take a 

 westerly bend for the same reason that the Gulf Stream 

 does so ; and in places where there are no great traces of 

 volcanic action we may expect to find evidence of the sea 

 gaining on the land from the south-west, as appears to be 

 the case, for instance, at St. David's. The eifects of this 

 reduction of the equatorial protuberance are, at all events, 

 worthy of more attention than they have hitherto received 

 from geologists. The amount of the reduction is, to a 

 large extent, matter of speculation, but the reduction itself 

 seems to be an ascertained fact. 



Whether the nebidar theory be accepted or otherwise, 

 most persons will concede that the earth was once too 

 highly heated to sustain life. From this fact, and what 

 we know astronomically about its cooling, some inferences 

 follow as to the early history of the earth which have 

 hardly been recognized. Assuming that, whenever the 

 necessary conditions for sustaining life are supplied, life 

 itself will speedily follow, we can in this way trace the 

 history of life on the earth. The Poles must have cooled 

 faster than the Equator, because they received less solar 

 heat. The earth, therefore, became habitable at the Poles 

 when the Equator was still too hot to sustain life. At this 

 early stage of intense heat a great part, if not the whole, 

 of the water on the earth was in the form of vapour. As 

 the cooling proceeded this vapour first formed two polar 

 seas, which gradually extended towards the l^quator as the 

 process of condensing the aqueous vapour went on. The 



I first form of terrestrial life was, thus, marine life in the 

 polar seas. This life must have been capable of existing 

 under a great atmospheric pressture, for the quantity of 

 vapour still suspended over the earth must have been 

 enormous. But some forms of marine life are found under 

 great pressure in the deep sea. This great blanket of vapour 

 no doubt moderated the extremes of temperature in summer 

 and winter, and thus assimilated the polar climate pretty 

 closely to that which now prevails in the tropics. Traces 

 of tropical vegetation in the Arctic regions need, therefore, 

 create no surprise. The only cause of surprise is finding 

 them where they were presumably deposited after the 

 earth had cooled down nearly to its present condition. 

 But we have no reason to conclude that the carboniferous 

 period, for instance, at the eightieth degree of north 

 latitude was nearly contemporaneous with the same period 

 at the fiftieth degree. Life had probably already gone 

 through several stages of progress at the Poles when it 

 made its first appearance at the Equator. The condensing 

 of the vapour in the atmosphere, commencing at the Poles, 

 would proceed gradually towards the Equator, thus inducing 

 a flow of water in that direction. This woiild be entirely 

 opposed to the flow of water caused by the slackening of 

 the earth's rotation, but both would combme to produce 

 a submergence of the land in our latitudes. The effect of 

 slackened rotation probably continued to a later period 

 than that of the condensation of vapour and its precipitation 

 in rain. Rain, again, must, no doubt, have preceded snow, 

 as liquid water preceded ice. 



As to the amount of heat received from the stars, there 

 can be no doubt that it has been different at difi'erent 

 times, but it may be doubted whether the difl'erence was 

 sufficient to produce a sensible change in the chmate of the 

 earth. Nevertheless, this possible explanation of certain 

 terrestrial phenomena should not be wholly overlooked. 



One further suggestion I may make. Suppose an 

 equatorial protuberance composed of solid land is formed 

 by the earth's rotation, and that this rotation subsequently 

 diminishes. It then becomes a great mountain chain, no 

 longer in equilibrium, but subject to a double pull to the 

 north and south. Assuming that the earth has a fluid 

 nucleus, might not this pull, assisted by some irregularities 

 in the shape of the range, lead to one half of the range 

 being pulled to the north of the Equator and the other half 

 to the south, the position of both the Poles and the Equator 

 on the earth's crust being thus displaced.' The mountain 

 chain would still form a circle round the earth, but would 

 become inclined to the Equator. I merely throw out this 

 hint for the consideration of those better versed in the 

 subject. The great Pamir Steppe is not far from 

 diametrically opposite to the highest part of the Andes 

 or Cordilleras. W. IL S. Mo.nck. 



aEOGRAPHY AS A SCIENCE IX ENGLAND. 



To the Editors of Knowleimie. 

 Sirs, — The programme unfolded by Dr. Mill in his 

 article on " Scientific Geography " in your last issue is 

 brilliant but ambitious. I should like to ask what shupe 

 his proposal would take, and whether any work on 

 similar lines has yet been done in Great liritain '? 



GK0(iR.4PHER. 



THE PUZZLE OF "26." 



Note. — We must oxpn'ss our n-gret to tliose convsiwiuliMit* who 

 Imve seut us further solutions of the im-eiiious puz/.h> of "ili " that 

 we are uuable to insert their eonimuiiioalions. in eonseiiueuee of a 

 reiiuest by Messrs. T. t^nlish k Co., of 9!), Fore Street, London, the 

 publishers of the puzzle, not to disclose any further solutions of it. 

 We have received many solutions, but we do not desin- to interfere wil li 

 the business of Jlessrs. T. Ordish & Co., even bv inadverten.-e. -Eds. 



