386 Searles V. Wood, Jun. — The Climate Controversy. 



earlier periods in which that form of life abounded were warmer 

 than the climates of the Tertiary group. So far as the lower types 

 of animal-life and the remains of vegetation furnish evidence, the 

 climate of Northern Europe during both the Eocene and Miocene 

 periods would seem to have been as warm as that of any preceding 

 period. Though so little evidence is thus, however, afforded by 

 organic remains, there is one fact that seems to me to bear upon the 

 subject which I have not seen alluded to, and it is this, viz. the 

 effect of increased heat over the earth's surface generally woiild, as 

 is well known, produce increased rainfall, and, as a consequence, 

 more rapid atmospheric denudation ; more sediment, that is to say, 

 would be carried down by rivers to furnish the material for sedi- 

 mentary deposits accumulating around continental areas. Now if 

 we compare such groups of rock as the Silurian with Tertiary groups, 

 we are struck with the smaller amount of change presented by the 

 forms of organic life in any given thickness of sedimentary deposit, 

 in the case of the older, than in the case of the newer formations ; 

 and, ceteris paribus, this would raise a presumption that sedimentary 

 deposit proceeded more rapidly during the earlier Geological periods 

 than it did during the later. 



No. 2. — It is obvious that no alteration in the obliquity of the 

 ecliptic would affect the quantity of heat received from the Sun by the 

 Earth as a whole. The effect, whatever it may be, would be con- 

 fined to the distribution of this heat in latitude. There appears to 

 be a unanimous opinion among astronomers up to the present time, 

 that the utmost limit within which the inclinations of the planes 

 of the equator and ecliptic to each other can vary is less than a 

 degree and a half ; ^ a quantity that seems too little of itself to have 

 affected climate to any great extent, whatever be the correct view as 

 to the kind of alteration which such variation would produce. Nor 

 would a decrease in the obliquity remove the difficulty offered by 

 long seasons of continuous night, which some geologists consider 

 irreconcilable with the fossil vegetation of Spitzbergen, unless it were 

 so great as to bring the plane of the equator to wdthin a very few 

 degrees of that of the ecliptic. Spitzbergen, lying in latitude 80° 

 North, and the sun taking just the same time for its passage from 

 the equator to the tropics, whether the obliquity be great or small, 

 the winter of Spitzbergen would not be very materially shortened, 

 unless the Arctic circle were brought to at least half its present 

 distance from that country. If, however, we suppose this to occur, 

 the obliquity being reduced from its present amount by as much as 

 one-third, it would still leave Spitzbergen far within the Arctic 

 circle ; and its light-receiving position even then would only be 

 about the same which that part of Greenland lying between the 

 74:th and 75th parallels of latitude now occupies. Such a reduction 



1 Sir C. Lyell, in his " Principles," states, however, that Sir John Herschel 

 informed him, that although the limit calculated by Laplace (1° 21') was true as 

 regards the last 100,0C0 years, yet if millions of years were taken into account, it was 

 conceivable that the variation might be found to extend to three, or even four 

 degrees. 



