W. Ferrel — Relative Temperatures of the Hemispheres. 89 



Then after another rise, "most probably near the close of the 

 Pliocene," "the faults increased their displacement, the vol- 

 canic vents reopened," and the Colorado River resumed the 

 operation of sinking its channel ; and, as time went forward it 

 made the inner chasm with all its grand features. The erosion 

 made quite rapid progress owing to the high pitch given the 

 surface by the new elevation; it has now almost ceased, the 

 river having nearly reached a level of slight change by erosion 

 or what is here called its base-level, — a base-level nearly for 

 the stream at the present state of elevation of the land and 

 ordinary annual floods. Captain Dutton observed that the 

 Glacier period intervened between the Pliocene and the present 

 time — a rain)- rather than an icy era for that district— increasing 

 the depth of the Canon and making some new channels; but, 

 he adds — limiting the effects more than some others might do, 

 in view of the fact that the head waters of the Colorado drain 

 the wide mountain region of the Rocky mountain summit for 

 a breadth from north to south of more than 300 miles, — 

 "The Glacial period appears to have been of too brief duration 

 to have achieved any very great results in this district." 



It was once thought,' and the idea still prevails almost uni- 

 versally, that the southern hemisphere of our globe is colder 



than the northern. This tirst arose from the comparison of 

 Dove's thermal charts for the two hemispheres. The observa- 

 tions upon which that of the southern hemisphere was based 

 extended only as far south as the parallel of 40° S. The com- 

 parison, therefore, between the two hemispheres could be made 

 for the portions only between the equator and the parallels of 

 d«i ""'. and so far as this comparison extends, the mean tempera- 

 ture of the southern is really .greater than that of the northern. 

 It was, however, tirst suggested bv Dove, and rendered still 

 m<>re probable bv the researches and theoretical considerations 

 <>)' Hopkins. Sartorms von Waltershausen, Forbes and others, 

 that the conditions may be reversed in the higher latitudes, 



hemisphere than in the northern. 



With a view of settling this question, and that of the 

 equality or incquaiitv of the mean temperatures of the two 

 hemispheres. Dr. Ilanu of Vienna'- has recently undertaken a 

 * Ueber die Temperature der siidlicben Hemisphare. Sitzb. der k. Akad dor 



