Igneous Ejections, Volcanoes. lil 
terial that constitutes to a large degree the deeper regions of 
the crust. 
There is, however, considerable diversity among true igneous 
rocks. Besides the prevalent doleritic iron-bearing kinds, i in- 
cluding dolerite, peridotite, melaphyre, etc., to which the pre- 
ceding observations relate, there are trachytic or feldspathic 
rocks whose constitution, especially in the case of the more 
siliceous varieties, comports with their origin from the fusion 
of granitic rocks or of sedimentary beds made of granitic ma- 
terial. They occur in the same regions in which doleritic 
dikes exist, as well as among volcanic products. 
Such a a composition does not, however, make it certain that 
the supercrust was their source, " for true granite and gneiss and 
even quartzites occur constituting old Archeean terranes, and 
it may be that essentially the same kinds of rock are to some 
extent represented in regions of the infra-Archzean crust and 
. even in the fire-seas. 
ina iste volcanic mountain of western u. nd at 
here the ejections are almost all basaltic, there are 
feldspathic lavas at the very summit of the dome about the 
summit crater. A sight of the boiling movements of Kilauea 
in 1840 led me to explain this association in volcanic moun- 
origin ; and another , of an i urentian) dolerite from Grenville, 
Canada, by Hunt Geol Re Rep. Levee Yee : 
ac G.= 296, Ii ay, 
ee Bir hg 47°80 49°40 fic 
"SEER Ce cee any 14:80 14°62 17°35 
Sesquiox. iron __._...__. rape ~ 9% sete 
Segre pele eat 1-40 13°08 16°21 se a 
Protox. manganese .__.__ 0°32 5-86 9 
ek 6°46 84 ne 
eit te een 10°56 12-89 10°34 10°19 
ESSE ee rere 2°60 48 de - 
06 0°86 0°34 
Volatile LG eee 1 19 1-41 gl oe 
100°2 100° 00°25 101°32 
' analysise says the fron is protoxide, though determined under the form of sesquioxide in his 
ep Present. (Princ e occurrence of trap’ hag all periods from “28 sogeaimenars = 
(Principles, chapt. vii); and Mr. S. Allport announ a recent 
wind Gorter May, -8i3) ented Tertiary and Paleozoic "Traps," that he has 
invesi ns 
blication the results of many in eustainin 
view which he aa on time main ined as to the reignite spor oot ae com- 
Position nm ~ a iy ‘of eruptive rocks of widely eo 
on this >. D204, 
269, B08 ays subject the author’s Geol. Report, wn 8 "fixped, 
