P Geology, &c. of the Connecticut. 
large a part of every country is covered with geest, and 
so imperceptible is the passage of some roéks into others, 
leaving the observer in doubt for miles which rock predom- 
inates, that after all, two equally good geologists would not 
probably fix the limits of different rocks precisely alike. 
And to exhibit all the minor salient aad reentering angles 
which any rock makes on the surface, would require a map 
on a scale five times larger than that used in the present 
instance. In attempting, therefore, to give every rock 
that position and extent on the map which it actually occu- 
pies on the surface, I do not suppose I have done any thing 
more than to approximate to the truth. It is hoped, howev- 
er, that the approximation : sufficiently close to answer 
most of the purposes of geology. | trust at least that this 
outline will furnish assistance . er pre ee geologists. 
In constructing this map I have derived very great assis- 
tance in the vicinity of New Havant from the researches of 
Professor Silliman, and of Dr. Percival. Indeed, could 
either of these gentlemen have been induced to form a map 
of that region, I should gladly have omted e souther 
part. In the northern part of the m 1 have eee assist- 
aiporante. 
The sides of the map are not precisely meridians; but 
incline 3 or 4 degrees to the right, as is evident from the 
fleur de iis attached to the upper right hand corner. The 
longitude and latitude are marked from those of Deerfield, 
which have been determined by numerous observations. 
Having made these preliminary remarks, I now proceed 
to describe the several rocks occurring in this district, in the 
order in which they are put down in the explanation ‘of the 
colours on the upper left hand corner of the map. 
1. GRANITE. 
Coloured purple—or a mixture of carmine, red, and 
Prussian blue. 
Almost every variety of this rock described by geolo- 
gists occurs in the region of the map, except the ‘ianaieit 
