Mr T. M. Reade, in his presidential address to the Liverpool Geological Society, discussed the question of 'geological time,' and took as an approximate measure thereof the denuding effect of rain-water on the earth's surface. The most rainy districts in England are those in which the oldest rocks prevail; but the average annual rainfall, including Wales, may be taken at 32 inches. Assuming the area of the two to represent one river basin, the quantity of water discharged in a year would contain more than eight million tons of solid matters; and at this rate, 12,978 years would be required to lower the surface of the land one foot. Analyses of sea-water shew that there are in 100,000 tons, 48 tons of carbonate of lime and magnesia, and 1017 tons of sulphate of lime and magnesia; and the ocean contains enough of the first to cover the whole of the land with a layer fifteen feet thick; and of the second to make a layer 267 feet thick. Twenty-five million years would be required to accumulate the one, and 480,000 years the other. Again, the total surface of the globe is 197 million square miles. A cubic mile of rock would weigh 10,903,552,000 tons; so that, as Mr Reade states, 'to cover the whole surface of the globe one mile deep with sediment from the land at the rate of 800 tons per square mile of land-surface, would take 52,647,052 years.'
Geologists have speculated over this question many years: it has now passed into the hands of mathematicians, without whose aid it will never be settled. The Rev. Dr Haughton, F.R.S., of Trinity College, Dublin, in a paper read before the Royal Society on the last evening of their session, 'On the probable age of the continent of Asia and Europe, and on the absolute measure of geological time,' says that the elevation of Asia and Europe from beneath the deep waters, separated the earth's axis of rotation from the axis of figure by 207 miles, which would produce a large amount of wabbling. At present, 'astronomers are agreed that the motion of the pole is secular and very slow, all traces of wabbling having disappeared.' Then after a series of mathematical demonstrations, the doctor continues: 'The geological age of the continent of Asia and Europe is well marked by the horizon of the Nummulitic Limestones,' which extend from the Mediterranean to Japan. 'These rocks make up the backbone of the great continent, and at its formation were raised from deep water to form the highest chains of mountains in the globe. Geologically speaking, they are modern, belonging to the Lower Tertiary Period. My calculations assign to the Nummulitic Epoch a date not less than 4157 millions of years ago. No practical geologist will feel any surprise at this result.'