GEOGNOSY OF THE APPALACHIANS. 481 
are found to be identical with those of the Levis formation,* and 
it is worthy of notice that although Sedgwick places the mica- 
schists with andalusite (chiastolite) so far below the graptolitic 
beds, he elsewhere, in comparing the rocks of North Wales 
Cumberland, states that the chloritic and micaceous rocks of 
being distinct from the other rocks of North Wales, and much 
older.t 
In Victoria, Australia, the position of the chiastolite schists, ac- 
cording to Selwyn, is beneath the graptolitic slates. Boblaye, it 
is true, asserted in 1838 that the chiastolite schists of Les Salles, 
near Pontivy in Brittany, include Orthis and Calymene,{ but when 
we remember that even experienced observers in the White Moun- 
tains for a time mistook for remains of crustacea and brachiopods, 
certain obscure forms, which they afterwards found not to be 
organic, and that Dana, in this connection, has ealled attention to 
the deceptive resemblance to fossils presented by some imperfectly 
developed chiastolite crystals in the same ion, § we may well 
require a verification of Boblaye’s observation, especially since we 
find that more recently D’Archiac and Dalimier agree with De 
Beaumont and Dufrenoy in placing the chiastolite schists of 
Brittany at the very base of the transition sediments, marking the 
summit of the crystalline schists. || 
With regard to the crystalline schists of Lakes Huron and Su- 
perior, to which the name of the Huronian system has been given, 
the observations of all who have studied the region.concur in plac- 
ing them unconformably beneath the sediments which are supposed 
to represent the base of the New York system, while, on the other 
hand, they rest unconformably on the Laurentian gneiss, fragments 
of which are included in the Huronian conglomerates. The gneissic, 
series of the Green Mountains had, however, as we have seen, been, 
since 1841, regarded by the brothers Rogers, Mather, Hall, Hitch- 
cock, Adams, Logan, myself and others, as of Silurian age. Eaton 
and Emmons had alone claimed for it a pre-Cambrian age until, in 
1862, Macfarlane ventured to unite it with the Huronian system, 
and Salter, Quar. Jour. Geol. Soc., xix, 135. 
te et ae ee ek, 664. 
