1870.] 67 [Jackson. 



climate at the north ages ago. Now what physical, cosmical, geolog- 

 ical or astronomical causes can be cited to explain a cooling below 

 zero of the earth in those regions ? 



Suppose it could be proved that the whole earth was reduced in 

 temperature to that low degree, what would follow? There would 

 be no evaporation of water adequate to the formation of snow thou- 

 sands of feet deep, and hence no glaciers could be produced even 

 were the other conditions also existent. 



Furthermore, it has been shown by recent experiments in France, 

 that if the rocky crust of the globe should be cooled universally below 

 freezing, all the water now existing on the earth's surface would be 

 absorbed by the pores of the rocks, for the water of our globe is kept 

 at the surface only by the internal heat of the globe, and cannot pen- 

 etrate beyond a depth of two miles without being returned as 

 steam, which condenses into water again. 



Indeed, it has been proved that if the interior of the earth consists 

 of rocks, and the temperature of the whole earth was reduced to the 

 freezing point, that five times the quantity of water now existing, as 

 oceans, lakes and rivers, would be absorbed by the rocks, and every 

 trace of humidity of the earth's surface would disappear; and fur- 

 thermore, that the porosity of the rocky strata would be equal to the 

 absorption, also, of the entire atmosphere, so that the earth would be 

 in the condition of the moon, without either water or air. 



This would hardly be a state of things favorable to the formation 

 of glaciers. 



We need not go so far as this to render improbable the exist- 

 ence of ancient glaciers in New England ; for the considerations be- 

 fore advanced are sufficient to create at least serious doubts, since 

 the requisite conditions for their formation are wanting. 



Glaciers form from partially melted snow on high mountains. In 

 Switzerland their lower limit, or line of perpetual snow, is nine thou- 

 sand feet elevation above the sea. A continuous supply of snow, 

 from evaporated water in warmer regions, is required to keep up 

 the supply in the elevated portions of the mountain. 



The movement of glaciers is determined by the slopes of the 

 mountains, the ice moving, as proved by Forbes, like a soft solid in a 

 trough. 



It is evident, also, that glaciers descend from mountains qua-qua 

 versal, that is, go in all directions as allowed by the mountain 

 slopes and gorges, and make their grooves and scratches in the rocky 



