CONCLUSION. 103 



Conclusion. 



Before dismissing the subject of tlie Taconic rocks, it will be useful to state very briefly a 

 few facts of a general bearing : 



1. This system is important in an economical point of view, in being the repository of the 

 white and clouded marbles : it is probably the only system in this country which contains any 

 marble suitable for statuary. 



2. It has already been stated, that it is this system which furnishes all the hematites and 

 black oxide of manganese. 



3. It is the most productive system for furnishing the white siliceous sand for glass, sawing 

 marble, etc., or a sharp-gritted material for sand paper. 



4. The belt of country traversed by the Taconic rocks is one universally productive : The 

 hills are generally susceptible of cultivation to their tops ; the valleys, which are underlaid 

 by limestone, are rich ; and though there is not a great depth of vegetable mould, the soil is 

 strong, and not soon exhausted : the land is suitable both for tillage and pasturage. 



5. An interesting fact will be observed in relation to the kind of boulders distributed over 

 this belt of country, viz. the extreme rarity of those belonging to the primary rocks. A few 

 appear along the eastern edge, adjacent to the gneiss and granite ; but towards the centre of 

 the formation, it is extremely uncommon to meet with one. This fact is not confined to a 

 small territory, but I beheve prevails through the county of Berkshire, and to a great distance 

 north. The boulders in part belong to the rocks of the Taconic system, and are mostly gra- 

 nular quartz, which resists for a great length of time the agency of the weather. Boulders 

 of limestone are extremely rare. 



6. The valleys of this system of rock are in character with the system itself ; they are 

 long and narrow. Thev have been formed probably by the combined operation of two dis- 

 tinct causes : 1st, by uplifts which have first fractured the strata ; and then, 2d, by excavation, 

 not wholly by the present water courses, but hj some more powerful means. The streams 

 which now flow in these valleys, are generally rapid, rarely sluggish, and more rarely furnish 

 imposing water falls. They are all subject to rise rapidly, and endanger bridges. Vast 

 amount of damage has accrued to the country lying in the range of this system of rocks. 



7. Since the general uplift of the country, very few disturbances have appeared to occur ; 

 and it is very remarkable that trap dykes and injected rocks of any description so rarely 

 occur. I have, for many years, passed over them in various directions, and I have never yet 

 seen an instance of the kind. 



8. The Taconic rocks appear to be equivalent to the Lower Cambrian of Prof Sedgwick, 

 and are alone entitled to the consideration of belonging to this system, the upper portion 

 being the lower part of the Silurian system. 



