20 RURAL NEW YORK 



high-calcium limestone, the Calciferous-Trenton. 

 It touches the Mohawk iiiver and passes under Lake 

 Ontario. Its widest development is in central Jef- 

 ferson County. On the soutli the next band of rock 

 is a succession of gray to dark blue shales and sand- . 

 stones known as the Hudson River group. They 

 swing east over the southwest flank of the Adiron- 

 dacks, along the Mohawk Eiver, and thence south- 

 ward through the Hudson Valley past the east slope 

 of the Catskill Mountains. These rocks form the 

 greater part of the floor of the Hudson Valley. 

 Their eastern development has been much folded and 

 contorted by mountain-making processes, so that 

 throughout the Hudson Valley and progressively to 

 the east line of the State the strata stand at a high 

 angle and sometimes on edge. By this means bands 

 of limestone were brought to the surface in a succes- 

 sion of pockets scattered through the valley. The 

 metamorphosing forces of pressure and heat incident 

 to the folding, changed the shale to slate, the sand- 

 stone to quartzite and the limestone to marble. All 

 of these occur in deposits of commercial importance. 

 South of Lake Ontario the floor of the plain is 

 formed by a quartzose sandstone and a gray or red 

 shale interbedded with red sandstone. The sand- 

 stone is sufficiently hard to be used for paving brick 

 and for building. This is the Medina, and reaches 

 up to the foot of the " Niagara Mountain." In the 

 Ontario Lake region of western New York many 

 of the farm houses are built of smooth rounded water- 



