LIME AND CEMENT INDUSTRIES 649 



and in Westchester and Dutchess counties the outcrops of the 

 crystalline dolomites are often found surrounded by an accumu- 

 lation of white sand. 



The position of the beds is a feature of considerable economic 

 importance, specially when those in a quarry are of different 

 quality. In the case of a steep dip the advantages are the pos- 

 sible extraction of the required layers without the necessity of 

 disturbing the others, while the disadvantages are increased cost 

 of hauling the rock to the surface, the deeper down we go, unless 

 the entrance to the quarry happens to be at a lower level than 

 that from which most of the stone is taken; with steeply dipping 

 layers the rock may be weathered to a much greater depth than 

 in the case of horizontal ones, because the upturned edges furnish 

 a ready means of entrance to the weathering agents. In the 

 extraction of individual layers the inclosing ones must be sup- 

 ported either by timbering or else by leaving pillars of rock; 

 and, as quarries operated in rocks with a steep dip are often apt 

 to go to much greater depth below the surface than other quar- 

 ries, there may be an increased cost for timbering. 



In the case of horizontal layers we have the advantages of 

 having the haulage of the rock nearly all at the same level; the 

 quarry will often drain itself ; there is much greater space to work 

 in and consequently the depth of the quarry can be much greater; 

 the rock as quarried can often be loaded directly on the cars, the 

 tracks being run into the quarry. The disadvantages of this 

 method are that, if only certain layers are required or can be 

 used, the upper ones have to be first removed in order to reach 

 the desired beds of stone so that there is often much stripping. 



This variation in dip must be carefully watched in some regions 

 where the rocks have undergone considerable folding, as in the 

 Hudson valley from Catskill to Kingston. Here at times the 

 beds are nearly vertical, while again, only a few hundred feet 

 farther, they may be nearly horizontal. Jointing has both its 

 advantages and disadvantages. While the presence of joints 



