The grand Colorado Canyon. 173 



it would be unfair to deny their denuding agency even in our 

 regions. There are so many phenomena near us which can 

 hardly be explained as effects of water and ice, but which be- 

 come easily intelligible as soon as we recognize dry air in motion 

 as a geologic force. There is perhaps not a spot on earth that 

 bears no trace of erosion ; neither, on the other hand, is there a 

 spot where the activity of wind denudation or deflation is en- 

 tirely absent. It is only a question of unbiased observation of 

 nature, and of not attributing to water things which it cannot 

 accomplish. 



How close together and in how intimate union erosion and 

 deflation act is shown by an eloquent exainple, the famous Colo- 

 rado canyon in Arizona. Most of the members of the great ex- 

 cursion expected that our way from the railway at Flagstaff to 

 the Colorado canyon would lead through a desert. What was 

 our surprise, therefore, when we found that it led for 120 kilo- 

 meters over a plateau more than 2,000 meters high, with prairies 

 and beautiful pine woods. The shady growth of Finus iwnderosa 

 extended to the very edge of the canyon gorge, and as we climbed 

 the last steep slope we were able to come within two steps of the 

 canyon without imagining how close Ave were to the coveted 

 goal. One step, and we stood on the verge of a gorge 2,000 

 meters deep, and only at a distance of 20 kilometers did we see 

 the steep verge of the other shore. A magic twilight as yet 

 reigned in the purple depth; only the topmost crags of some 

 rocky towers burned with the rosy glow of the rising sun. Our 

 eyes SAvept along the horizon, and as far as they could reach 

 there appeared an uninterrupted mantle of forest; only toward 

 the southeast the snoAV-covered peak of mount San Francisco 

 emerged like another Etna, AAdiile toAvard the north, more than 

 200 kilometers aAvay in an air-line, arose the gourd-like mount 

 Navajo. Again we looked doAvn into the fathomless depth, 

 gradually illumined by reflection from the upper peaks glitter- 

 ing in the sunlight. The rock walls seemed to glow as with 

 transparent light, and only with difficulty could the eye distin- 

 guish details. Little by little the purple glow and the deep blue 

 shadoAVS of the abyss disappeared, and as the sun rose higher 

 and higher, the shadows grcAV shorter. Like jutting battlements 

 and fairy-like palaces, one rock structure after another disclosed 

 itself. At last Ave were able to scan the steep Avails, to recognize 

 with complete distinctness the Cambrian unconformity, and even 

 at one point to see the river rushing along. 



