[1. “The Great Ice Age,” p. 26.]
mingled in the débris which they deposited. This is not the case. The unstratified Drift is unfossiliferous, and where the stratified Drift contains fossils they are the remains of land animals, except in a few low-lying districts near the sea.
“Over the interior of the continent it contains no marine fossils or relics."
“Not a single trace of any marine organism has yet been detected in true till."
Moreover, if the sea-waves made these great deposits, they must have picked up the material composing them either from the shores of the sea or the beds of streams. And when we consider the vastness of the drift-deposits, extending, as they do, over continents, with a depth of hundreds of feet, it would puzzle us to say where were the sea-beaches or rivers on the globe that could produce such inconceivable quantities of gravel, sand, and clay. The production of gravel is limited to a small marge of the ocean, not usually more than a mile wide, where the waves and the rocks meet. If we suppose the whole shore of the oceans around the northern half of America to be piled up with gravel five hundred feet thick, it would go but a little way to form the immense deposits which stretch from the Arctic Sea to Patagonia.
The stones of the “till” are strangely marked, striated, and scratched, with lines parallel to the longest diameter. No such stones are found in river-beds or on sea-shores.
“We look in vain for striated stones in the gravel which the surf drives backward and forward on a beach,
[1. Dana’s “Text-Book,” p. 220.
2. “The Great Ice Age,” p. 15.]
and we may search the detritus that beaches and rivers push along their beds, but we shall not find any stones at all resembling those of the till."
But we need not discuss any further this theory. It is now almost universally abandoned.
We know of no way in which such waves could be formed; if they were formed, they could not find the material to carry over the land; if they did find it, it would not have the markings which are found in the Drift, and it would possess marine fossils not found in the Drift; and the waves would not and could not scratch and groove the rock-surfaces underneath the Drift, as we know they are scratched and grooved.
Let us then dismiss this hypothesis, and proceed to the consideration of the next.
[1. “The Great Ice Age,” p. 69.]
WAS IT CAUSED BY ICEBERGS?
WE come now to a much more reasonable hypothesis, and one not without numerous advocates even to this day, to wit: that the drift-deposits were caused by icebergs floating down in deep water over the sunken land, loaded with débris from the Arctic shores, which they shed as they melted in the warmer seas of the south.