Searles V. Wood, Jun. — The Climate Controversy. 387 



in the obliquity, therefore, although it would take those parts of 

 Greenland near Disco, about latitude 70°, in which a similar fossil 

 vegetation is preserved, out of the Arctic circle, and consequently 

 out of the limits within which darkness for any lengthened period 

 prevails, would not remove the difficulties presented by the Spitz- 

 bergen vegetation in any appreciable degree. 



Two writers, Colonel Drayson and Mr. Thomas Belt, have lately 

 urged that the Glacial period proper was due to an increase in the 

 obliquity of the ecliptic ; but Mr. Croll insists that, instead of an 

 increase of cold during the year in high latitudes, or even an 

 increase of winter cold balanced by a corresponding increase of 

 summer heat resulting from an increase of obliquity, the effect of 

 such increase would be to augment the warmth of the polar climate 

 as a whole, by reason that the further the sun receded from the 

 equator, the more heat he would during summer impart to high 

 latitudes at the expense of low ones, while the cold of winter would 

 not be materially aggravated in high latitudes by his greater reces- 

 sion on the opposite side of the equator ; and he quotes Mr. Meech's 

 calculations to prove that the poles would, when the admitted 

 obliquity was at its maximum, receive during the year nineteen rays 

 for every eighteen which it receives at the present time. It seems to 

 me, however, notwithstanding this, that there is some fallacy lurk- 

 ing in the contention that the winter cold would not be augmented 

 by an increase of obliquity to the same extent that the summer heat 

 would be. Moreover, if the reasoning which Mr. Croll uses to 

 prove that there is a cumulative tendency in the formation of ice 

 and snow, and consequently of cold, in relation to the Excentricity 

 theory which he advocates, be sound, is it not equally applicable to 

 the Obliquity theory ? and inasmuch, therefore, as the area of the 

 polar circles, or the area in which ice and snow form and remain 

 during winter, would be increased by a greater obliquity (and this 

 in a larger degree than the obliquity itself), would not the effect of 

 that increased area, by the cumulative process, make itself felt in a 

 general refrigeration of climate ? If so, then, by parity of reasoning, 

 a diminution of this area of cumulative cold, by a decrease in the 

 obliquity, should produce amelioration of climate. There will be 

 occasion to recur to this subject of the accumulation of cold in 

 considering the cause No. 3. Taking the view he does, however, as 

 to the effect of an increase in the obliquity, Mr. Croll attributes 

 much influence to it, in combination with the cause to which he 

 refers the greatest influence on climate — the varying excentricity of 

 the earth's orbit ; and he contends that, assuming that the astrono- 

 mers are right in limiting the variation in the obliquity to about 

 1° 22' on each side of the amount at which it stood at the beginning 

 of the present century, a concurrence of the maximum of this 

 obliquity with the maximum of excentricity would probably cause 

 forest-trees to grow at the pole of that hemisphere which had the 

 sun in perihelion during winter. 



No. 3. — The cause suggested under this head is the one which, 

 during the past few years, has produced the greatest amount of dis- 



