448 Searles V, Woodj Jun. — The Climate Controversy. 



but as there seems so mncli uncertainty as to the results which 

 would flow from an alteration in the obliquity, the difficulty of 

 forming any idea as to the change in the climate of any given spot 

 of the Earth's surface from a given change in the axis of rotation 

 appears to be great. 



No. 6. — The cause suggested under this head, that of variations in 

 the Sun's heat, has had the advocacy of Professor Balfour Stewart. 

 The theory derives support from the spectroscopic researches made 

 of late years into the constitution of the Sun and fixed stars ; and 

 more particularly from the circumstance that a sudden increase in the 

 brilliancy of one of the latter some few years since was discovered, by 

 means of the spectroscope, to be due to an outburst of incandescent 

 hydrogen ; that is, to an outburst of the element which constitutes the 

 rose-coloured prominences observed on the Sun's limb during eclipse. 

 These outbursts of hydrogen are believed to be identical with the 

 spots on the Sun ; and these spots are so far connected with climate, 

 that some astronomers are inclined to the belief that Mr. Meldrum's 

 theory of their frequency being connected with corresponding periods 

 of Cyclone frequency has some foundation. If variations in these out- 

 bursts can be connected in ever so slight a degree with meteorological 

 phenomena, it is a legitimate inference that far greater variations, 

 extending over prolonged periods of time, may have had proportion- 

 ately greater, and longer continued influence upon the meteorological 

 conditions of the Earth's surface ; in other words, on Climate. If the 

 view entertained by geologists (until the discovery of beds alleged 

 to exhibit evidences of glacial conditions in various old formations 

 raised contrary ideas), that a generally warmer climate prevailed 

 during geological periods prior to the Glacial, were true, we should, 

 in the theory under consideration, regard the Sun as having under- 

 gone at a very late period of the Earth's history an abnormal reduc- 

 tion of its heat-emitting power, from which it is now slowly 

 recovering. So far as regards these alleged glacial deposits of 

 remote geological periods, abnormal reductions in the Sun's heat at 

 those periods would seem as legitimate a cause for them as any other 

 to which they have been assigned; but the same geological diffi- 

 culties and contradictions which beset these alleged deposits, and 

 raise so much doubt as to their being really due to glacial action, 

 would be as inexplicable under the theory we are considering, as 

 under any other. 



Mr. Croll has objected to it, that this theory would not 

 account for interglacial periods of warmth ; but, as it seems to me, 

 without sufficient reason ; and believing as I do, and as I have in 

 discussing the Excentricity theory explained, that the English 

 Glacial and post-Glacial beds indicate at most two (and possibly 

 only one) oscillations of climate since the commencement of the 

 Glacial Period, I cannot discover anything in the evidences of that 

 period repugnant to the theory under consideration ; for if not 

 merely a few stars occasionally blaze out and shortly after diminish 

 to their former splendour, but many others are undergoing, as is 

 believed, smaller and more gradual changes in lustre, there seems no 



