24 NEW YORK STATE MUSEUM 



The manufacture of paving brick requires first of all a clay that 

 can be vitrified without difficulty and when so treated possess great 

 hardness and toughness. Experimentation has demonstrated that 

 the consolidated clays known as shales yield the best results in these 

 respects, and consequently such clays are almost universally em- 

 ployed, although in certain cases the admixture of other- clays may 

 be needed to impart all the desired qualities to the product. 



In its shale formations New York State has an inexhaustible and 

 widely distributed resource which may be made the basis of an in- 

 dustry large enough to supply all the local requirements in paving 

 material of the best quality. The value of the resuurce has been 

 recognized by private enterprise, and for the last twenty-six years 

 paving brick has been manufactured on an increasingly large scale, 

 with a production last year of 35,666,000 having a value of $576,- 

 970. The local product comes in competition with that made in 

 Pennsylvania, Ohio, Michigan and other states, and the test of ex- 

 perience generally appears to justify the opinion that the brick made 

 in the New York plants compare favorably with the best in the 

 market. 



Practically the whole of the southern half of the State, between 

 the meridian of Buffalo and Albany and the Pennsylvania state 

 line, is underlain by formations that include shale among the more 

 important members. Not all of these, however, are adapted to pav- 

 ing brick manufacture, since the requirements in this case are much 

 more restricted than in most branches of the clay-working industry. 

 It may be said that the shales best suited for this purpose are found 

 in the higher or more southerly formations which are generally rec- 

 ognized under the names of the Hamilton, Portage and Chemung 

 groups. All these are distributed in belts that extend east and west 

 across the central and lower tiers of counties. There are a great 

 number of sites where the shales outcrop in force and appear to be 

 adaptable to the purpose in view, but it would require detailed inves- 

 tigations in the field and some experimentation to determine just 

 what localities offer the best advantages. The chemical analyses of 

 clays and shales give comparatively little information as to their 

 working qualities in the manufacture of paving brick. The follow- 

 ing table of analyses is given, however, in an attempt to show some- 

 thing of the composition of the various clays and shales that have 

 been used, are used, or may have some future application in the 

 manufacture of vitrified ware. 



