Page:Popular Science Monthly Volume 68.djvu/317

Rh After exhibiting to their own satisfaction the inadequacy of either the iceberg or the glacial hypothesis to account for their production, the authors attempted to show how all the phenomena might be explained by the theory of a sudden discharge of a portion of the Arctic Ocean southward across the land. They discussed the important functions of the 'wave of translation,' showing its surpassing velocity and great propulsive power, and traced the influence of vehement earthquakes near the pole in dislodging the northern waters and ice and maintaining in the rushing flood these vast and potent waves. They then suggested that, at a certain stage of the inundation, the ice, previously floating free, might impinge with irresistible violence against the tops of submerged hills, and that the Canaan Mountain stood precisely in the position to take the brunt of the ice-driving flood as it swept down the long, high slope of the distant Adirondacks and across the low, broad valley of the Hudson.

They then proceeded to show that, at the instant when some enormous ice island struck the crest of the mountain and scooped the trench which we there behold, a great vortex was produced by the obstruction thus suddenly thrown in the path of the current, which, endowed with an excessive gyratory or spiral velocity, was capable of sustaining and carrying forward the greater part of the fragments. As in the instance of the waterspout and the whirlwind, the whirlpool would gather into the rotating column the projected blocks and strew them in a narrow path in the line along which its pendent apex would drag the ground.

Truly there were catastrophists in those days!

Agassiz, it will be remembered, came to America in 1846, and in 1847 was appointed to the professorship of geology and zoology in Harvard. Naturally, an attempt was made to apply his views on glaciation to the phenomena of the drift in America. In the summer of 1848, in company with Jules Marcou and a party of students, he undertook the exploration of the Lake Superior region, the results of which were published in 1850. The views set forth relating to the glacial phenomena of the region are of paramount interest.

He argued that the drift of all northeast America and northwest Europe was contemporaneous and due to a general ice sheet. Through a repetition of many of his former arguments, he showed that a current of water sufficiently powerful to transport the large blocks found would have swept practically over the entire globe and not have stopped abruptly, as did the drift, after reaching latitude 39° north. This limit of distribution of the boulders to the northern latitudes also indicated to his mind that the matter of climate was an important factor. Water-transported material, he argued, would not cause straight furrows and scratches, and the theory that such might be due to drifting icebergs was rejected on the ground that existing bergs were