1884. 93 Trans. N. V. Ac. Set. 



if the conditions as to elevation continued to the north of us, it would 

 not be necessary to go far to find perpetual snow. For snow once fallen 

 or ice once formed, would never melt, but, accumulating through the 

 ages, would force its way south by its own weight, until it reached so 

 fa; below the true snow line as to be melted. 



Such uplifts to-day, the atmosphere remaining as it is, and the 

 earth's axis again becoming perpendicular, would bring back the 

 Glacial epoch. 



The warmth of the Champlain was due to a reversal of these con- 

 ditions. From some cause the axis had attained its present obliquity, 

 this of itself rendering the climate of polar regions more genial, 

 while the depression of the land below its present level, and the con- 

 sequent extension of ocean surface, greatly aided and accelerated the 

 result. 



A moderate and comparatively local uplift, mostly confined to the 

 eastern continent, would account for the minor Glacial period which 

 seems almost confined to that part of the world. 



Subsequent changes of elevation left us the climate of to-day. 



SUMMARY. 



1. The early warmth was due to the " blanket" of carbonic acid, 

 aqueous vapors, and probably other gases and vapors. 



2. The uniformity — lack of seasonal changes, and the equality of 

 liglit and actinic force — was due to the axis of the earth being nearly 

 or quite perpendicular. 



3. The slow fall of temperature at first, the more rapid fall in later 

 times, and the cold of the Glacial epoch, were due to the gradual puri- 

 fication of the atmosphere, and, with reference to the cold, to great 

 high latitude uplifts. 



4. The return of warmth was due to increased obliquity of axis, and 

 to high latitude depression of the land and consequent extension of 

 the ocean. 



5. The Champlain warmth was due to the extreme depression. 



6. The minor Glacial epoch was due to comparatively sudden and 

 local elevation. 



7. Present climate is due to present arrangement of land and water 

 and to the introduction of seasons, or, in other words, to the present re- 

 lation of day and night. 



The influence of vapors and gases on climate was pointed out by 

 Prof. Tyndall and others. Several have proposed a change of incli- 

 nation or of geographical position, as a solution of the climatic problem. 

 Dana and others have spoken of the high latitude uplifts and the sub- 

 sequent depression. The theory in this paper weaves all these and 



