S Geology, ^-c, of the Connecticut. 



large a part of every country is covered with geest, and 

 so imperceptible is the passage of some rocks 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 sahent and 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 is sufiiciently close to answer 

 most of the purposes of geology. 1 trust at least that this 

 outHne will furnish assistance to succeeding geologists. 



In constructing this map I have derived very great assis- 

 tance in the vicinity of New-Haven, 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 omitted the southern 

 part. In the northern part of the map, I have been assist- 

 ed by Dr. J. A. Allen, Lecturer on Chemistry in Middle- 

 bury College, and by Rev. J. Andrews, of Putney. Dr. 

 E. iEmmons, of Chester, has also communicated facts of 

 importance. 



The sides of the map are not precisely meridians ; but 

 incline 3 or 4 degrees to the right, as is evident from the 

 flcur de lis 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 cctrmine, red, and 

 Prussian blue. 



Almost every variety of this rock described by geolo- 

 gists occurs in the region of the map, except the transition 



