70 NEW YORK STATE MUSEUM 



terial into a hard, hydrous silicate of lime, which binds the sand 

 grains together. The amount of lime used varies from 5 to 20 

 per cent depending on the purity of the sand. 



Although several patented systems of manufacture are on the 

 market, the general scheme is not patented and the manufacture 

 of the brick can be undertaken by any one. In fact several 

 American companies have recently entered the field with their 

 own systems and no patents. 



The estimated cost of a well equipped plant with a capacity 

 of 20,000 brick, per 10 to 12 hours, is estimated by Mr Peppel 

 to range, in Ohio, independent of site and buildings, from 

 $20,000 to $25,000. 



The cost of production in the United States, exclusive of de- 

 preciation in plant, interest on investment, loss of time in 

 breakdown and repairs, etc., according to the same author, 

 varies from $3 to $4 per 1000. The selling price ranges from $8 

 to $15 per 1000. 



From a large series of tests made, Peppel considers sand- 

 lime brick to be strong and durable and in all respects a safe 

 and reliable building material. 



SLATE 



BY HENRY LEIGHTON 



The slate belt of New York State occupies an area extending 

 from the Poultney river, the northern boundary of Washington 

 county, south to the Batten kill, and from the Vermont border 

 west a distance varying from 6 miles in the northern to 12 

 miles in the southern portion. The majority of the active quar- 

 ries are in the central part of the field, in Granville township. 

 Under a slight covering of glacial drift and soil, the rocks of the 

 belt consist of a series of Cambric and Ordovicic sediments, 

 greatly metamorphosed and intricately folded. They are made 

 up of limestone, shale, slate, quartzite and sandstone members, 

 with slate predominating. The original bedding of the slates 

 has been partially obliterated by the metamorphism and in its 

 stead a pronounced cleavage has been developed. The dip of 

 the cleavage planes is very steep, usually 45 or more. The 

 original bedding planes can often be distinguished in the slates 

 as bands or ribbons of varying color. 



The slates vary in color, red, purple, mottled and green slates 

 being found in the belt. Of these the red is the most valuable, 



