Geology and Natural History. 393 
tive origin. He goes so far as to state that even the most com- 
plicated system of nia ahe at? dykes may by pressure be altered 
a conformable series of schists. Konondin ng to the author’s 
view, the granulite was originally an intrusive mass which impreg- 
nated the surrounding sediments and lo wen 4 metamorphosed those 
t a greater distance, but itself cooled far below the surface. 
it converted the impregnated slates into gneisses and the others 
into mica schis 
e extensive role attributed to sediments, broken and again 
nted by eruptions of graniti¢ material, thus forming rocks 
sericite schists he regards as produced from acid eruptive rocks, 
while others, indistinguishable from them, were once sediments. 
Little justice can be done to this ‘elaborate me moir, Whose every | 
page is full of de rete in the Lbs esent short notice, and cae ne 
we can only refer the reader to the work itself, w , whatever 
€ one’s geological beliefs, cannot but repay a arefal perusal, 
In conclusion, too hig ise cannot be bestowed upon the 
photographie illustrations of rock structures, taken in part by 
wihpintene, light from but little magnified microscopic sections, 
art by reflected light from carefu wae polished hand speci- 
men dias whey permit of a study which is hardly less grigcente 
ep would be that of the original specim 
» Os Be on the origin of bedding in reas ee ats fom rocks, 
by James D, Dana.—The views presented in the nahh of Dr. Leh- 
mann, noticed above by Professor G. H. Williams, are of so 
much interest that I add here some illustrations of the chief 
point from my observations in America, where gavreted cart rocks 
rely pee, under very varied conditions over large are I 
43 (as Prof. Williams states), previous to making these ober 
vations having but a year before arrived in this country afte 
four years sities spent partly among volcanic islands of she 
ac otis and on portions of its voleanic borders, I put forth the 
by | sects that granite areas had been volcanic Senter, and that 
eisses, or schists, about such an area were portions of the 
PE a outflow At that time I thought well of the new i ea, 
for I had seen vibe saeke that were schistose. Wider experi- 
* This Journal, xlv, 104. 
