482 Scientific Intelligence. 
occurring as a constituent of some igneous rocks) “the labrado- 
rite or anorthosite” rocks of the Adirondacks and British ries pi: 
probably “ represent the volcanic and intrusive rocks of the Lau 
rentian period.” 
These conclusions as a ee rocks make the mineral labra- 
ould be set- 
tled by geological pieamtigntion ; for we rightly ask that volcanic 
origin should be proved by the presence of obvious volcanic or 
eruptive conditions, What there is in a lime-and-soda feldspar to 
make its presence proof of eruptive origin, or of the existence of 
great volcanoes in a region that shows no other evidence of it, no 
one has pointed out. Lime is an exceedingly common material in 
sediments; and soda or sodium is present. in other feldspars, and, 
in the state of chloride, abounds in sea water and occurs in salines 
some metamorphic rocks that have nothing of volcanic origin in 
their constitution, as the writer has shown to be true in the vicin- 
ity of New Haven, Connecticut. So with felsyte, a rock made up 
of common feldspar or orthoclase, with often quartz-—its compost 
sketches, 
ous beds of the Quevee up. The a soap by the Green 
ain region to the south in Verm d Massachusetts, 
ae out by Mr. Wing and the writer, a on the latter ques 
epoch in widely ated regions.” “No better instances of 
such difference couid be cited than the Mesozoic and Carbonifer- 
ous formations of British Columbia, and those of the same a riods 
in Eastern America and od Siluria n and Cambrian formations 
contains a large amount of im- 
ical and economical, With re- 
wy 
