MEMOIR OP CLARENCE EDWARD DUTTON 
13 
impressed by Richthofen’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 1875Jx> 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 I 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 — that of radioactivity — was made in 1897. 
which seemed to furnish the explanation of the necessary amount of heat near 
the earth’s surface.” 
His final conclusions on volcanoes and radioactivity were presented to 
the Hational Academy of Sciences, April 17, 1906 (26). 
