374 



CEMENTS, LIMES, AND PLASTERS. 



When dealing with the Lehigh district cement rock, the steam- 

 shovel is not quite so satisfactory, for much of the rock will require 

 hand sledging after being blasted before it can be conveniently handled 

 by the shovel. The hard limestones are still more intractable, and 

 often require not only sledging but reblasting. This, of course, greatly 

 decreases the financial effectiveness of the shovel, and in many quarries 

 will entirely prevent its use. In shallow quarries vertical seams filled 



FIG. 79. Steam-shovel handling limestone. 



with clay, soil, or other wash from the surface may greatly hinder the 

 work of the shovel; and in quarries where rock is so mixed in compo- 

 sition as to require sorting the shovel is worse than useless. 



Crushing and drying in the quarry. The rock is usually transported 

 directly to the mill just as quarried, except that the larger masses are 

 sledged to convenient size for handling. At a few quarries, however, 

 a crushing-plant is installed at the quarry, and the rock is sent as crushed 

 stone to the mill. Several of the quarries in question sell a certain 

 portion of their product as road metal, which, of course, reduces the 

 cost of the finer material which is sent to the cement-plant. 



A few plants have also installed their driers at the quarry and dry 

 the stone before shipping it to the mill. This practice, shows a saving 

 in mill space, but otherwise it seems to have little to recommend it. 



