Woeikoff, a Russian meteorologist, and one of the ablest critics of Mr. Croll's theory, and to whom we are indebted for these facts, ascribes the greater present warmth of the northern Atlantic basin, not to the astronomical cause invoked by Mr. Croll, but to the relatively small extent of sea in the middle latitudes of the northern hemisphere. The extent and depth of the oceans of the southern hemisphere would of themselves give greater steadiness and force to its trade-winds, and lead to a general lowering of the temperature; so that it is doubtful if the astronomical causes introduced by Mr. Croll, even with Dr. Ball's re-enforcement, would produce any appreciable effect while the distribution of land and water remains substantially what it is at the present time. Still another variation in the astronomical theory has been set forth and defended by Major-General A. W. Drayson, F. R. A. S., instructor in the Royal Military School at Woolwich, England. He contends that what has been called the precession of the equinoxes, and supposed to be "a conical movement of the earth's axis in a circle around a point as a centre, from which it continually decreases its distance,"[DW] is really a second rotation of the earth about its centre. As a consequence of this second rotation, he endeavours to show that the inclination of the earth's axis varies as much as 12°; so that, whereas the Arctic and Antarctic Circles and the tropics extend to only about 23° from the poles and the equator, respectively, about thirteen thousand five hundred years ago they extended more than 35°; thus bringing the frigid zones in both cases 12° nearer the equator than now. This, he contends, would have produced the Glacial period at the time now more generally assigned to it by direct geological evidence. [Footnote DW: Untrodden Ground in Astronomy and Geology, p. 26.] The difficulty with this theory, even if the mathematical calculations upon which it is based are correct, would be substantially the same as those already urged against that of Mr. Croll. It is specially difficult to see how General Drayson would account for the prolonged temperate climate in high northern latitudes during the larger part of the Tertiary epoch.