OF THE NORTHWESTERN STATES. 5 



thing quite different. And yet, this has occurred in the drift, and must therefore 

 be due to a phase of the drift phenomena. The rocks beneath the superficial 

 materials in which these cavities are formed, are everywhere polished and grooved 

 by the drift forces. 



At the foot of the Alps, moraines are formed mechanically, by the movements 

 of glaciers, carrying forward earth and stones, which are finally left in rounded 

 heaps on the more level country. Masses of ice become entangled with the loose 

 materials, which in due time melt away and disappear. 



I assume it to be a settled point, that the moving force in the drift epoch was 

 glacier ice. Nothing else seems to be adequate to the results we observe. The 

 objections to this view have been removed by the observations of Dr. 1. 1. Hayes, of 

 the Kane Arctic Expedition, and of Dr. Eink. On the northAvest coast of Green- 

 land, which is a vast glacier, the ice is found to be advancing toward the coast over 

 a country comparatively level. It has accomplished a movement not only down 

 inclined surfaces, such as the slopes of mountains and along flat land, but even up 

 acclivities that were opposed to its progress. If the temperature of Greenland or 

 the Arctic Circle were brought down to latitude 40° north, glaciers Avould exist, in 

 fact, they now occur within 45° of the equator. It is only necessary to suppose the 

 northern hemisphere during the ice period to have been covered with continental 

 ice, to the depth of many hundred feet, as Greenland is now. 



This frozen expanse must have been attacked by the heat of the sun most power- 

 fully on the side of the equator. Its southerly limit being at latitude 40°, it would 

 be along this edge that it would be first melted. The conditions of movement in 

 glacier regions would then be supplied, only the field would be a larger one. 



On the north, the extent of the mass would be such, that in that direction, there 

 could be no movement, and the expansion must produce its whole effect in a south- 

 erly direction. Thus, so far as resistance in the rear gives rise to motion in front, 

 a fixed mass of ice may be considered equivalent to a central mountain chain. 

 Admitting such a state of things, it follows that along the southern edge of this 

 all-pervading glacier, fragments and masses of ice would be inclosed in, and buried 

 beneath, the drift materials. Sir John Richardson in 1849-50, while journeying 

 down the Mackenzie river, discovered ice at different depths beneath the surface of 

 the earth, extending to several hundred feet. Although potatoes were raised in 

 the soil at Fort Hope, it did not thaw during the short summer months more than 

 two or three feet in depth. It is reported that in Patagonia, huge piles of stones 

 and ice are seen mingled together for years. The first impression on viewing these 

 depressions of the drift is, that they are due to subsidence. 



In the cases just cited, if the mixed mass consisted more of ice than of earth 

 and stones, the surface should be one of pits and depressions. Hillocks or moraines 

 coxdd only occur in such materials where the earthy and imperishable parts are in 

 excess. When the proportions are about equal, there would be both cavities and 

 moraines. In the southerly part of Wisconsin, both forms are observed, but as we 

 proceed northerly the depressions increase in number, and the hillocks or ozars, 

 diminish. As we proceed northerly, there is less of stratification, and a closer 

 approach to the true glacial moraines. The drift cavities in other parts of the 



