364 J. D. Dana on the Quartzte, Limestone, etc., 
sion of Logan, that the great disturbances affecting these Lower 
Silurian rocks occurred at the close of the Lower Silurian. 
I propose to discuss the facts as to the special age of these 
rocks on another occasion. 
I have said that the conformable superposition of the lime- 
stone, schists, and quartzite is unquestionable—contrary to the 
ain rocks. The evidence consists in the direct testimony of 
sections showing unmistakable superposition. 
In my discussion of the subject, I first briefly explain 
the topography of the region, in order that the positions and 
peoemrnicn, relations of the several localities described may 
appreciated. The accompanying map (Plate IV) in its out- 
lines is a reduction of the Berkshire County map of 1858; the 
topography I have added from such observations as I have 
been able to make without the use of instruments. I next 
describe the kinds of rocks in order that their variety and 
their transitions may be understood, and also the bearing of 
the facts on the value of lithological characters as a criterion 
geological chronology. Finally, I shall present the facts con- 
nected with the stratification of the rocks, as obtained from see- 
tions in different parts of the region. 
1. Topography. 
In the vicinity of Great Barrington (see the map) there are 
three principal north-and-south valleys over a region about ten 
miles wide, each containing strata of crystalline lhmestone. 
(1.) The western, that of I ont (and western part of Great 
a is backed, as just stated, by the Taconic mountams. 
(2.) The central is that of the Housatonic river, on which are 
situated the villages of Great Barrington; Van Deusenville, 
two miles north of Great Barrington; Housatonic, two miles 
farther north; and Stockbridge, three miles northeast of 
Housatonic, or six from Great Barrington. 
(3.) The eastern, the valley of Muddy Brook and the Kon- 
ats lies along the eastern border of the town of Barrington, 
and has Beartown Mountain on the eas 
The two ranges of ridges between these three valleys ae 
sist mainly of the metamorphic schists and quartzite whic 
overlie, or are interstratified with, the limestone. : 
e range bounding the Housatonic valley on the west 38, by 
estimate, 100 to 250 feet in height above the river. ae 
Van Deusenville it consists of two overlapping parts, Land W, 
and betw ows Williams river. 
The range on the east of this valley varies from 100 
least 500 feet in elevation above the Housatonic. To the 
northward it bends more to the westward toward the Hous 
