BLUEISTONB AND OTHER SANDSTONES 7 



spar, more or less stained with iron. The cementing material 

 is probably silica, as dilute hydrochloric acid has no effect, and 

 it is not stained with iron.^ 



Joints and bedding 



The beds of stone are divided naturally by vertical joints at 

 right angles, one system running about north and south, while 

 the other has an east and west direction. The north and south 

 joints are known to the quarrymen as " side seams,'' while the 

 -east and west joints are called " heads," " head-offs " or 

 " headers." These joints are persistent throughout the whole 

 area of the two main districts, but in Delaware and Broome 

 counties the east and west joints are likely to be very irregular. 

 The distance between these joints determines the maximum size 

 of the blocks, but not often is a stone the full size of the block 

 taken up. These joints are from 5 feet to 75 feet apart as a 

 rule. The bed is divided also by horizontal seams which are at 

 varying distances apart. These layers are known as " lifts." 



In addition to these open seams and between them, occur 

 what are known as " reeds." The reeds are really closed seams 

 w^hich can be seen on looking closely at the edge of a block. 

 The reeds are both an advantage and a disadvantage. They 

 occur, as a rule, in only the fine grained stone. They are advan- 

 tageous in that they provide means of splitting a thick stone 

 into a number of thinner ones. This splitting is done by means 

 of a " point " and thin wedges. They are a disadvantage in that 

 they are a source of weakness in the stone. The frost will often 

 open up the reeds, specially in curb which is set on edge. Each 

 <]uarry has its characteristic reeds. A typical " black reed " is 

 the best for splitting stone. 



It is often true of these reeds that, after quarrying, when 

 the stone is exposed to the weather two or three weeks before 



'The test was as follows. A thin slice of the stone, tSo of an inch thick 

 was immersed in the dilute acid. In the case of a calcareous sandstone, 

 or of a ferrugrinous sandstone, the grains of silica and feldspar would 

 have been loosened into sand. The slice of rock remained practically 

 imaffectod. 



