SURFACE GEOLOGY. 67 



which we have record, and geologists and physicists have been reaching 

 out for some broader and more powerful influence than any terrestrial 

 changes could produce. The objections to Lyell's theory are simply its 

 insufficiency ; and while no one questions the fact that very considerable 

 changes of climate could be produced by altering the arrangement of con- 

 tinents and seas, it seems hardly possible that so great variations of cli- 

 mate as those under consideration could be effected by the most radical 

 re-distribution of territory. The advocates of Sir Chas. Lyell's view hardly 

 realize, as it seems to me, that if the land surface of the globe was con- 

 centrated in a belt in the tropics, the distribution of heat from the tropics 

 to the poles would be almost exclusively through the medium of the 

 atmosphere, for the great system of oceanic circulation which now pre- 

 vails would then be totally abrogated. But it is more than doubtful 

 whether much heat could be carried from the tropics into the arctic re- 

 gions through the agency of the winds, since the upper strata of the atmos- 

 phere are very cold, and heated air rising from the tropical land would 

 soon be cooled, and thus the influence of such land could not reach far, 

 either north or south. It seems to be well established, also, that the pres- 

 ent diffusion of tropical heat is chiefly through the agency of ocean cur- 

 rents, such as the Gulf stream, and these ocean currents all spring from 

 a great equatorial current which passes from east to west across the 

 Atlantic and Pacific oceans. From this, branches, which are great ocean 

 rivers of warm water, flow off north and south, forming circles in each 

 half of each great ocean. The motive power of this system of oceanic cir- 

 culation is apparently derived from the equatorial belt of trade-winds, 

 which derive their motion, from east toward the west, from the slight 

 lagging of the atmosphere in the rapid rotation of the earth's surface. 

 Hence it is evident that if we were to fill the interval between the tropics 

 of Capricorn and Cancer with land, the transfer of heat through this me- 

 dium would be arrested. 



Another argument against the Lyellian hypothesis may be drawn from 

 observed geological facts. As I have before stated, the proof is abundant 

 that in the Miocene Tertiary epoch a warm-temperate climate prevailed 

 as far north as the shores of the Arctic sea. But we know that at that 

 time the land area in the arctic regions was scarcely less extensive than 

 now ; and that the outlines of the central and southern portions of the 

 continent have changed but little since then. Hence we are justified 

 in saying that no changes in the land area of North America have taken 

 place since the Tertiary age which could be regarded as the cause of the 

 great changes of climate which are distinctly recorded in the Quaternary. 

 It may also be said that no stronger confirmation of Lyell's theory can be 



