CHAPTER XVII.

FORMER GLACIAL EPOCHS.—REASON OF THE IMPERFECTION OF GEOLOGICAL RECORDS IN REFERENCE TO THEM.

Two Reasons why so little is known of Glacial Epochs.—Evidence of Glaciation to be found on Land-surfaces.—Where are all our ancient Land-surfaces?—The stratified Rocks consist of a Series of old Sea-bottoms.—Transformation of a Land-surface into a Sea-bottom obliterates all Traces of Glaciation.—Why so little remains of the Boulder Clays of former Glacial Epochs.—Records of the Glacial Epoch are fast disappearing.—Icebergs do not striate the Sea-bottom.—Mr. Campbell’s Observations on the Coast of Labrador.—Amount of Material transported by Icebergs much exaggerated.—Mr. Packard on the Glacial Phenomena of Labrador.—Boulder Clay the Product of Land-ice.—Palæontological Evidence.—Paucity of Life characteristic of a Glacial Period.—Warm Periods better represented by Organic Remains than cold.—Why the Climate of the Tertiary Period was supposed to be warmer than the present.—Mr. James Geikie on the Defects of Palæontological Evidence.—Conclusion 266