Cambrian Conglomerate of Islay and North-west of Scotland.—Ice-action in Ayrshire and Wigtownshire during Silurian Period.—Silurian Limestones in Arctic Legions.—Professor Ramsay on Ice-action during Old Red Sandstone Period.—Warm Climate in Arctic Regions during Old Red Sandstone Period.—Professor Geikie and Mr. James Geikie on a Glacial Conglomerate of Lower Carboniferous Age.—Professor Haughton and Professor Dawson on Evidence of Ice-action during Coal Period.—Mr. W. T. Blanford on Glaciation in India during Carboniferous Period.—Carboniferous Formations of Arctic Regions.—Professor Ramsay on Permian Glaciers.—Permian Conglomerate in Arran.—Professor Hull on Boulder Clay of Permian Age.—Permian Boulder Clay of Natal.—Oolitic Boulder Conglomerate in Sutherlandshire.—-Warm Climate in North Greenland during Oolitic Period.—Mr. Godwin-Austen on Ice-action during Cretaceous Period.—Glacial Conglomerates of Eocene Age in the Alps.—M. Gastaldi on the Ice-transported Limestone Blocks of the Superga.—Professor Heer on the Climate of North Greenland during Miocene Period 292 CHAPTER XIX. GEOLOGICAL TIME.—PROBABLE DATE OF THE GLACIAL EPOCH. Geological Time measurable from Astronomical Data.—M. Leverrier’s Formulæ.—Tables of Eccentricity for 3,000,000 Years in the Past and 1,000,000 Years in the Future.—How the Tables have been computed.—Why the Glacial Epoch is more recent than had been supposed.—Figures convey a very inadequate Conception of immense Duration.—Mode of representing a Million of Years.—Probable Date of the Glacial Epoch 311 CHAPTER XX. GEOLOGICAL TIME.—METHOD OF MEASURING THE RATE OF SUBAËRIAL DENUDATION. Rate of Subaërial Denudation a Measure of Time.—Rate determined from Sediment of the Mississippi.—Amount of Sediment carried down by the Mississippi; by the Ganges.—Professor Geikie on Modern Denudation.—Professor Geikie on the Amount of Sediment conveyed by European Rivers.—Rate at which the Surface of the Globe is being denuded.—Alfred Tylor on the Sediment of the Mississippi.—The Law which determines the Rate of Denudation.—The Globe becoming less oblate.—Carrying Power of our River Systems the true Measure of Denudation.—Marine Denudation, trifling in comparison to Subaërial.—Previous Methods of measuring Geological Time.—Circumstances which show the recent Date of the Glacial Epoch.—Professor Ramsay on Geological Time 329 CHAPTER XXI. THE PROBABLE AGE AND ORIGIN OF THE SUN.