TRANSACTIONS OF SECTION C. 723 



7. On the improhabilitij of the theory that former Glacial Periods in the 

 Northern Hemisphere were due to Eccentricity of the Earth's Orbit, and 

 to its Winter Perihelion in the North. By W. F. Stanley, F.G.S., 

 F.B.Met.Soc. 



The theory of Dr. Croll, accepted by many geologists, is that former glacial 

 periods in the Northern hemisphere were due to greater eccentricity of the earth's 

 orbit, and to this hemisphere being at the time of glaciation in winter perihelion. 

 This theory is supported upon conditions that are stated to rule approximately at 

 the present time in the Southern hemisphere, which is assumed to be the colder. 

 Recent researches by Ferrel and Dr. Hann, with the aid of temperature observations 

 taken by the recent Transit of Venus expeditions, have shown that the mean tempera- 

 ture of the Southern hemisphere is equal to, if not higher than, the Northern, the pro- 

 portions being 15 - 4 C. Southern, 15 - 3 0. Northern. The conditions that rule in the 

 South at the present time are a limited frozen area about the South Pole, not ex- 

 ceeding the sixtieth parallel of latitude ; whereas in the North frozen ground in 

 certain districts, as in Siberia and North-Western Canada, extends beyond the 

 fiftieth parallel; therefore by comparison the North, as regards the latitude in 

 which Great Britain is situated, is at present the most glaciated hemisphere. As 

 it is very difficult to conceive that the earth had at any former period a lower 

 initial temperature, or that the sun possessed less heating power, glaciation in the 

 North could never have depended upon the conditions argued in Dr. Croll's theory. 

 The author suggested that trlaciation within latitudes between 40° to G0° was pro- 

 bably at all periods a local phenomenon depending upon the direction taken bv 

 aerial and oceauic currents ; as, for instance, Greenland is at present glaciated, 

 Norway has a mild climate in the same latitude, the one being situated in the pre- 

 dominating Northern Atlantic currents, the other in the Southern. Certain physical 

 changes briefly suggested in the distribution of land might reverse these conditions, 

 and render Greenland the warmer climate, Norway the colder. 



8. On Ice-Agc Theories. By the Rev. E. Hill, M.A., F.G.S. 



On the Montreal Mountain, in the neighbouring quarries, at the mouth of the 

 Saguenay River, and more or less everywhere over all Canada and all the north 

 and north-west of this continent, are seen phenomena which imply a former vastly 

 extended action of ice. The like are found over Europe and Asia, thus completely 

 encircling the pole. Many theories have been propounded to account for these 

 facts. It is proposed to pass these before you in review. 



Any explanation ought to account not only for cold greater than the present, 

 but for accumulations of snow and ice. .V kindred phenomenon is the greater size 

 of the Antarctic ice-cap. The supposed interglacial warm periods, and the un- 

 questioned luxuriance of Miocene vegetation in Greenland, ought also to find their 

 causes in any thoroughly satisfactory theory. 



The theories which have been propounded fall into three groups, as Cosmical, 

 Terrestrial, and Astronomical (or Periodical). 



The Cosmical theories are Poisson's Cold-Space theory — incomprehensible ; and 

 the Cold-Sun theory of S. V. Wood and others — lacking any evidence. 



The Terrestrial theories are numerous. Lyell's suggestion of Polar-continent 

 and Equatorial-ocean is opposed by evidence that continents and oceans lay on 

 much the same areas as now. The contrary view, Polar-ocean and Equatorial-land, 

 would deserve consideration but for the same opposing evidence. The elevation 

 view (Dana, Wallace), which alleges greater altitude of mountain-chains, 

 disagrees with the strong evidence for land-depression dining the period. The sub- 

 mergence view of Dr. Dawson agrees with this evidence, but requires elucidation. 

 Alteration of ocean-currents (Gunn, J. S. Gardiner) is a most powerful agency, but 

 would act locally rather than universally round the pole. Alteration of prevalent 

 winds, hitherto worked out by no one, deserves attentive consideration. Conditions 

 are conceivable which would produce over an area winds from cold quarters almost 



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