RICHER SOILS OF BERKS COUNTY. 505 



It is probable that this sandstone contains some 

 alkaline matter, which the water dissolves out of those 

 varieties which disintegrate so readily, which gives to 

 the harder varieties the property of withstanding the 

 fire, and has been instrumental in aiding the conversion 

 of the more changed parts into close and compact 

 quartz. 



Over this Potsdam sandstone lies the Black River 

 limestone of the New York geologists the lower Appala 

 chian of the valleys of southern Pennsylvania and Virginia, 

 where it is 4000 feet thick. In this border county of 

 Massachusetts this limestone has a less thickness, but, like 

 the sandstone, it is altered, and in many places is changed 

 into a pure white marble. It is generally rich in mag 

 nesia. The same rock is observed to be so also in the 

 Appalachian valleys. Here it is interstratified with beds of 

 mica and other altered slates. These hard rocks crumble 

 less readily, and form opener soils, than where the same 

 rocks occur in a softer and less altered condition. It is 

 of the mixed fragments of these rocks, however, that the 

 productive soils are composed, by which, as I have said, 

 this county of Berks is distinguished. The geological 

 map shows that these mixed limestone and altered clay 

 rocks occur in this county ; and hence we should infer a 

 greater natural fertility than the rest of the State pos 

 sesses. The comparatively great height of the Berkshire 

 valleys, and the altered character of the rocks, diminish 

 the productive character of the soils which in other locali 

 ties they produce. Here again, therefore, as in so many 

 other places, we are taught that, in addition to what the 

 mere inspection of a geological map conveys to us, the 

 physical character of the rocks themselves, and the 

 altitude of a place above the level of the sea, are among 

 the circumstances we require to learn before we can 

 venture to draw conclusions, or to pronounce opinions as 

 to what the agricultural character of a region really is. 



