92 WALKS AND TALKS. 



volcano exhibits, perhaps, a greater explosive energy than the 

 ancient one, and hence it may disperse greater volumes of 

 ashes ; yet some of the ancient volcanoes, near the beginning 

 of modern geological history, have ejected vastly greater quan- 

 tities of ashes than have been known to escape during any 

 eruption of historic times. Let us make the acquaintance of 

 some of the most remarkable of lava-covered areas. 



Let us turn, first, to what is probably the most extraordi- 

 nary outflow of lava lying on the earth's surface. A concise, 

 but comprehensive description has been furnished by Pro- 

 fessor Joseph Leconte: "Commencing in middle California as 

 separate streams, in northern California it becomes a flood 

 flowing over and completely mantling the smaller inequalities, 

 and flowing around the greater inequalities of surface ; while 

 in northern Oregon and Washington it becomes an absolutely 

 universal flood, beneath which the whole original face of the 

 country, with its hills and dales, mountains and valleys, lies 

 buried several thousand feet. It covers the greater portion 

 of northern California and northwestern Nevada, nearly the 

 whole of Oregon, Washington, and Idaho, and runs far into 

 Montana and British Columbia on the north. Its eastern and 

 southern limits are not well known, but its extent can not be 

 less than one hundred and fifty thousand to two hundred 

 thousand square miles, with a thickness of three thousand to 

 four thousand feet in its thickest part, where cut through by 

 the Columbia River. In another place, at least seventy miles 

 distant, where cut into twenty-five hundred feet deep by the 

 Des Chutes River, at least thirty successive sheets may be 

 counted." 



The Columbia has cut through the entire breadth and 

 depth of the Cascade range, down to within one hundred feet 

 of sea-level. Here is a canon one hundred miles long, with 

 the summits of the range rising twenty-five hundred to thirty- 

 eight hundred feet above the river surface. The entire walls 

 of the canon are composed of ancient lava. When we reflect 

 that the peaks of the Cascade range are simply results of 

 erosion, we can well believe that the highest summits were 



