The second rotation as defined consists in the pole of the heavens describing a circle around a point which is ascertained to be situated six degrees distant from the pole of the ecliptic. And it is asserted that by a knowledge of the second rotation it is proved that a variation of twelve degrees in the extent of the arctic circle and the tropics occurred not later than 13,500 B.C., “the tropics varying in distance from the equator from the minimum of 23° 25′ 47″ to the maximum of 35° 25′ 47″, thus extending the torrid zone during its widest expansion from Cape Hatteras to the river Plate.... It is calculated that at this date we are about 403 years distant from the time when the pole of the heavens in its revolution, the pole of the ecliptic and that of the second rotation, will be in the same colure,—that is, in the year 2,295 A.D.; and then the least differences in temperature between summer and winter will be experienced. From that time forward this difference will increase, and about 6,000 years later, or about the year 8,300 A.D., the earth will enter the next glacial period, and attain its greatest severity about the year 18,136 of our era.” General Cowell does not state how the widening of the tropical zone, as above set forth, would bring about a glacial period. The winters of the temperate zones would evidently be colder than now; but, on the other hand, the summers would be proportionally warmer, while the westerly winds above the latitudes of 40° would prevail the same as now.
Therefore, their general effect on the surface waters of the ocean in the high latitudes would not be changed with such an extension of the tropical zone, neither would the trade winds change their general direction with a wider torrid zone; yet the boundaries of the trade winds and also the westerly winds would be more shifting according to the declination of the sun, such winds being governed as now by the position of the sun during the summer and winter solstice. Yet the natural process for moving tropical water into the high latitudes, or excluding it therefrom, would not be greatly changed.
Consequently, the expansion of the torrid zone to the latitudes named by General Drayson would not affect the climate of the hemispheres sufficiently to cause a frigid epoch. On the contrary, the summer monsoons, which now blow from the north-east, along the shores of Eastern Africa, and also along the coast of Southern Brazil, would be much stronger with a vertical sun in midsummer as far south as river Plate, thus forcing the surface waters of the tropical oceans into the higher latitudes with greater facility than at this age.
Moreover, according to the statements of General Cowell, the present period of mildness should be on the increase, and obtain perfection in the year 2,295, or about 400 years hence; while, on the contrary, according to the explanations we have given in the preceding pages, there is much to show that an ice age is advancing, and has made considerable progress in the high latitudes of both hemispheres. Furthermore, if the second rotation, as claimed by General Cowell, is able to perfect a glacial period at regular intervals of 31,600 years, it seems that traces of frigid epochs should not be confined to late geological records, as there appear to be little or no traces of glacial work prior to the Quaternary or Post-tertiary periods.
It appears that explanations so far given, which depend on the astronomical theory to account for the ice age, are not in harmony with well-known geographical facts. The explainers neglect the attention due to the great prevailing winds which since the earlier geological ages have, in connection with continents, moved the surface waters of the ocean from torrid latitudes to colder zones, and from the colder zones to the warmer latitudes.
This exchange of ocean waters between the zones is as old as the continents which shape their courses. The important change wrought in the ocean currents sufficient to have caused the glacial age which ended the early warm epochs was brought about through the action of the prevailing winds, which, in connection with the form of continents, became able to move the ocean waters from the northern hemisphere into the southern sufficient to submerge the low lands of the southern hemisphere, causing a great diversion of the tropical currents from the high southern latitudes, such as I have pointed out in preceding chapters.
Those writers who believe that ocean currents have been the cause of great climatic changes have suggested that the existence of an ancient channel through the isthmus of Panama would have caused a frigid period on lands bordering on the northern shores of the Atlantic by turning the head-waters of the Gulf Stream into the Pacific Ocean.
Professor Agassiz thinks that such a channel existed during some remote geological age, judging from the semblance of the fauna pertaining to the Caribbean Sea and Pacific Ocean.
Yet it may be said that an open channel through Central America would have connected two high sea-levels.
For this reason there would be little or no exchange of water between the Caribbean Sea and the Pacific Ocean.