Wadsworth.] 
100 
[November 17, 
“Mr. Dana said he recognized also the action of cold water as supposed 
by Prof. Emmons, and cited a bed of clay at the foot of a basaltic hill in 
New South Wales, containing nodules of siliceous matter, which he sup- 
posed proceeded from the decomposition of basalt.” (Am. Jour. Sci., 1843 
(1), xly, 142). 
Later Professor Dana states : 
“ In this Journal, Yol. xly, p. Ill (1843), the writer has supported the 
principle that metamorphic changes require no other cause but what attends 
submarine igneous action, * * * *. The views then presented prop- 
erly include not only the heat from submarine volcanic action and fissure 
ejections, but the escape of heat, going on for ages, through the fractures 
attending the gradual folding and uplifting of strata while beneath the sea.” 
(Am. Jour. Sci., 1847 (2), iv, 92.) 
Again it is written : 
“ These facts illustrate two important points: 
1. That ordinary waters upon and through the earth’s surface are con- 
stantly active in dissolving and decomposing minerals and rocks; and that 
even species reputed indestructable are thus acted upon. 
2. That the waters are thus furnishing themselves with chemical agents 
for effecting other changes. These waters penetrate all rocks, as well as 
percolate through soils, or run in streams over the earth’s surface. Hence 
the action is a universal one, everywhere going on ; and the results are 
universal.” (System of Mineralogy, Ed. of 1854, page 227.) 
We come, in 1873, to the period of change in Professor Dana’s 
views : 
“ Portions of the erupted viscid material might have encountered water 
on the way to the surface, and thus have become penetrated with it; so that 
the viscid material at the high temperature became altered in part — * * * 
* * * Or else, this kind of change may have taken place through infiltra- 
ting waters. The fact that the vesicular trap (now amygdaloidal) is that 
which is hydrated, renders it rather probable that while zeolites and calcite 
may have been later made within the rock by superficial action or infiltra- 
ting waters, the chief change was contemporaneous with the eruption; for 
the vesicular character was undoubtedly then produced, and it was probably 
dependent on the same moisture that, penetrating the rock, caused the 
metamorphism or hydration through the mass. ******** The 
secondary origin of the zeolites and chlorite found to penetrate some dolerite 
and other kinds of igneous rock, as well as filling the cavities within them, 
