2 ON CHANGES IN THE DISPOSITION able period must have elapsed belore this earth, thus empty, was fitted for the reception of at least, terres trial life. Soil must have been prepared for vegetables; and that soil was the produce of time; though, in ad dition to the submarine alluvia of the previous ocean, many portions of the land must have retained the allu vium and soil of a former period, since I have shown that there could have been no revolution in which some dry land did not remain. At what periods animals and vegetables were placed in this renovated earth, physical evidence does not enable us to discover: and it must be remembered that, on this subject, the enquiries of Geology are properly and purely physical. If deduc tions are to be formed from them in support of the Historical records, they can have no value but by main taining the physical enquiry pure. To fabricate sys tems out of historical records, and then to use them in support of those very records, is a species of logic which seems to have taken refuge in geology when abandoned everywhere else. While the land of the original earth was higher than the present, the ocean was deeper. Time has shal lowed, and is still shallowing, these seas, and levelling these mountains; it is changing the outlines of our continents; and in rendering the rocky surface more extensively habitable, it is also enlarging it, as it will continue to do while the earth shall endure. He who shall divest the present surface of all but its rocks, who shall exterminate from our maps the great alluvial plains and deltas of the globe, with the countless in terior tracts of the same nature, will produce a sketch of the original earth, in no small degree interesting. It is through decomposition and disintegration, aided by mechanical power, that these changes have been pro duced. Whatever other causes have aided, the waste of the rocks, and the transference of their materials,