438 CLAYS AND CLAY INDUSTRY. 



ingredients of a mixture. In addition to this, the clay miner him- 

 self often does not know the exact use of the different clays dug 

 in his pit, especially when they are shipped to distant points. He 

 is, however, usually familiar with the burning qualities of the 

 several clays found on his property, and when there is a call for 

 a certain, type of clay, supplies samples which he considers will 

 most nearly answer the requirements. 



METHOD OF CLASSIFICATION. 



In treating Middlesex county, the scheme that has been adopted 

 is to group the clays primarily according to their refractoriness, 

 and under this according to kinds. It will do' no harm, there- 

 fore, to repeat the classification given in Chapter IV, under Fusi- 

 bility. The groups there made were : 



Highly refractory clays, fusing above cone 33. These include 

 the best of the so-called No'. 1 fire clays. 



Refractory clays, fusing at cone 31 to cone 33 inclusive. They 

 include some of those marketed as No. 2, and some of those sold 

 as No. 1. 



Semirefractory clays, fusing at cone 27 to 30 inclusive. The 

 lower grades of fire clay, including some sold as No. 2, the fire 

 mortars, wad and some sagger and stoneware clays, fall under 

 this head. 



Clays of low refractoriness fusing at cone 20 to 26 inclusive. 



Nonref ractory clays fusing below cone 20. 



The classification above outlined may meet with the disap- 

 proval of some clay miners in the Middlesex district, for some 

 clays called No. 1 will fall here in the second group, the refractory 

 clays. When we consider, however, that the terms No. 1 and 

 N01. 2 clays as applied throughout the whole Middlesex clay dis- 

 trict mean very little, it seems perfectly reasonable to adopt a 

 classification, the meaning of which is definite, even though the 

 lines drawn may be somewhat arbitrary, and perhaps not satis- 

 factory to all. 



