Searles V. Wood, Jun. — The Climate Controversy, 449 



reason for denying that our Sun may 'during a long period of 

 abnormal diminution have undergone one or more alternations, which 

 for thousands of years restored it, if not to its normal heat-emitting 

 state, yet partially to that state ; and in this partially abnormal 

 state it may still remain. 



Another objection raised by Mr. CroU to this theory is, that it 

 could not produce a Glacial Period ; because, since a reduction of 

 the Sun's heat would cause a reduction in the evaporation, there 

 would be less snow and rain fall, and consequently less snow and 

 ice to accumulate at the polar regions, and so produce glacial con- 

 ditions ; and he quotes a dictum of Prof Tyndall that more, rather 

 than less heat from the Sun is required to produce a Glacial Period, 

 what is really needed for that being condensers sufficiently powerful 

 to congeal the vapour generated by the heat of the Sun. Whatever 

 weight there may be attaching to this objection, it seems to me to 

 resolve itself into one connected with the cumulative effect of snow 

 and ice as an agent in producing glaciation ; for it is hard to under- 

 stand that an absolute diminution in the Sun's heat should not be 

 attended with a general refrigerence of the earth's surface, though 

 it were attended, as of course it must be, with a diminished fall of 

 condensed vapour. It seems to me that this diminution would be 

 principally sensible in the amount of rainfall, rather than snowfall , 

 but be this as it may, a diminished snowfall, so far from being a 

 difficulty in the way of the evidences presented by the Glacial 

 Period in Britain, would in my view be the reverse ; because, while 

 the height to which the Antarctic bergs rise above the water, coupled 

 with their form, and the known specific gravity of ice, leave little 

 doubt that the Antarctic land-ice from which they are detached 

 cannot be less than 5000 feet in thickness, the evidences presented 

 by the Glacial beds of England show that the thickness of the land- 

 ice which enveloped the northern part of Britain during the Glacial 

 period could not have exceeded a third of this amount. The 

 reasons which induce me to think this are too long to be given here ; 

 but I may mention that the Boulder-clay of England, and the huge 

 masses of white marl, or reconstructed chalk, acres in extent, which 

 occur in the mud and silt of the contorted drift of Norfolk, are in 

 my opinion formed of sheets and masses of the degraded material 

 produced by the land-ice transported at the bottom of the bergs and 

 dropped on the sea-bottom. Had these bergs detached themselves 

 from land-ice of such enormous thickness as that for which some 

 geologists have contended, we should require a corresjDonding depth 

 of water to have floated them, whereas we have no evidence of any 

 submergence in these parts sufficient to allow bergs of greater ver- 

 tical dimensions than 1500 feet to float. 



So far as abridged seasons of darkness are necessary, as some 

 think, to account for the rich vegetation, especially the evergreen 

 forms of tree in high latitudes, the theory under consideration 

 offers no solution of the difficulty ; and if the much greater warmth 

 of these latitudes were due to it, we must infer that the temperature 

 of medium and low latitudes would be proportionately increased ; 



DECADE II. — VOL. III. — NO. X. 29 



