MEMOIR OF CLARENCE EDWARD DUTTON 13 



impressed by Bichthofen's order of succession in the eruption of massive 

 rocks, beginning with propylite, a rock of intermediate composition, and 

 followed by two series, one a lighter but less fusible acid series ending in 

 rhyolite, and the other, a heavier though more fusible basic series, ending 

 in basalt. 



By a comparison of the chemical composition, density, fusibility, and 

 physical aspects of these igneous rocks with one another and the lighter 

 rocks up through which they were erupted, Dutton was led to the conclu- 

 sion that "it is the gross weight of the overlying cover of solid rocks 

 which presses the lava upward through any passage where it can find 

 vent" (page 131, Geology of High Plateaus), and that the succession is 

 a double sequence determined by density and fusibility. Concerning the 

 origin of this view in his own mind, Dutton remarks (footnote, page 131, 

 Geology of High Plateaus) : 



"It was when I was contemplating the great distances traversed by slender 

 basalt streams in southern Utah that this theory suggested itself to me. I had 

 no doubt that such lavas must have been ejected at a temperature much more 

 than sufficient to melt them. This seemed to contrast powerfully with the 

 habits of trachytic masses. It occurred to me then that this high temperature 

 might be absolutely essential to the eruption of so dense a rock as basalt, 

 while, a considerably lower one would suffice for lighter rocks. Immediately 

 the higher melting temperature of the rhyolites and trachytes suggested itself, 

 and almost as quickly as I write it the theory took form in my mind and the 

 double function of density and fusibility associated itself with a double se- 

 quence." 



In a letter October, 1911, he writes : 



"The subject of volcanoes and volcanic action had become of paramount in- 

 terest to me, and I resolved to grapple with the problem. All existing theories 

 seemed to me insufficient, and I became a confirmed skeptic as to the cause of 

 volcanic action. 



"From 1875 to 1885 I continued to labor with the problem, but could only 

 conclude that the cause was the local accumulation of heat ; yet no reason for 

 it appeared. For a time it seemed possible that the intrusion of basaltic 

 masses among the sedimentaries might lead to chemical reactions which would 

 furnish the necessary heat, as Prof. Reginald A. Daly so ably proposes in his 

 recent theory of volcanic action. But after long reflection 1 could not accept 

 that view, and concluded that as science then stood a solution was Impossible, 

 and it would be necessary to wait until some discovery should put another 

 face upon the subject. 



"A discovery of prime importance— thai of radioactivity was made in 1897, 

 which seemed to furnish the explanation of the necessary amount of beat near 

 the earth's surface." 



His final conclusions on volcanoes and radioactivity were presented t«> 

 the National Academy of Sciences, April 17, 1906 (26). 



