12 Messrs. Foster and Whitney on the 
the geology of the whole of the Lake Superior Land District, 
commencing with those formations which are the lowest in the 
scale of geological succession, or those which were first formed, 
and ascending to t which are now in the progress of accumu- 
lation. We shall only allude to the results of the former part of 
the report, so far as it may be necessary to enable the reader to 
form a connected idea of the geology of the whole region. 
The following table exhibits the names and the order of suc- 
cession of the geological groups which have been recognized as 
existing within the limits of our district. 
Classification of the Rocks. 
} sree 
Syenite. 
\ sree and Quartz rock, 
Plutonic 
Rocks. 
Of Various Ages. 
IGNEOUS. 
Greenstone, or Dolerite, Porphyry- 
Peete | Basalt, = daloid. - 
rnblende and Serpentine Rocks. 
Voleane [ies of f Spectr and Magnetic Oxyd 
Gneiss and Hornblende Slat 
C lorie,” Patedbi and Argillaceous ‘Slate. 
Beds of Quartz and Saccharoidal Marble 
METAMORPHIC, 
ponies, ennai 
7 
( Potsdam Sandstone. 
pai he Sandstone, 
ZY sto 
2 e 
Lewis Bids ye Limestone 
i. 
FORMATIONS. 
Ajlurian System. Galena Lim 
{ Hudson- nite Gecais 
Clinton Group. 
Upper. oe Group. 
ondaga Salt Group. 
Devonian System. Upper Helderberg Series. 
= 
E 
> 
| 
| 
AQUEOUS. 
Aw 
: Beds of Sand, Clay and Gravel rudely stratified. 
Drift System. | ‘Transported Blocks of Granite, Gre nd tone, dc. 
| Atte ial Deposits, 1 Spits buses bias 4 bore 07 Marshes, Flats, Hooks, 
ithe New York geologists have divided the Silurian system, as 
developed in that state, into eleven groups, while some of the 
Western geologists recognize, in its western extension, but five. 
pala the two systems of classification there is no community 
of na 
The ‘gccishihiid} position of our district is such as to form a 
connecting link between the east and the west. While, on the 
