REPORT. 



PART I. 



ECONOMICAL GEOLOGY. 



To His Excellency Levi Lincoln, Esq. 



Governor of Massachusetts. 



Having in a good measure executed the commission received from 

 your Excellency, bearing date June 25, 1 830, and directing me to 

 make a geological examination of the State ; I beg leave to present 

 you with the first part of my Report. 



My commission contemplates an exhibition of the different rock for- 

 mations in the State, upon the map of the Commonwealth now in 

 progress. But as it must necessarily be a period of considerable 

 length before that work can be completed, I have constructed a small 

 map from such materials as already exist, and delineated upon it the 

 various kinds of rock that prevail in the State. These are shown by 

 different colors and simple markings, easily understood by reference 

 to the tablets on the lower part of the sheet. 



To avoid confusion, I have placed on this map only so much of 

 topography and geography, as was absolutely necessary. All the 

 mountains and smaller rivers, with the boundaries of the towns, have 

 been omitted ; the centre of each town being indicated by a small 

 circle. For the same reason, I have employed only six different 

 colors to mark the rocks ; although more than twenty kinds are rep- 

 resented. But these, with a few exceptions, may be grouped together, 

 as they are in nature, in general divisions ; the rocks in each division 

 being so intimately related, that in an economical point of view, they 

 may be regarded as varieties ; although, in a scientific point of view, 

 their differences are very important. All the rocks of a group have 

 a common color on the map ; and the different sorts are delineated by 

 means of dots, crosses, circles, &c. In short, it has been a great ob- 

 ject with me, so to simplify the map as to render it easily intelligible ; 



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