METHODS OF WORKING CLAY DEPOSITS. 33 



with a steam shovel than by hand. Wheel scrapers are also 

 employed at times, and, if the distance to the dump heap is short, 

 the material can be carried there in the scraper. If the stripping 

 can be used to mix with the clay, it is sometimes dug with 

 shovels and screened to' free it from pebbles, A method tried 

 at some localities is to remove the sandy or gravelly overburden 

 by washing. This is done by directing a powerful stream of 

 water from a hose against the face or surface of the gravel 

 and washing it down into some ditch along which it runs off. 

 In selecting the site for a dump heap', care should be taken 

 not to. locate it over any clay deposit which is to be worked out 

 later, but the presence or absence of such clay under the pro- 

 posed dump can commonly be determined by a few bore holes 

 made with, an auger. 



•■'•.' — ~- : - •Jancly c!a.y 



Tonewure clay 



ffefort clay 

 Fire clay 2 



Fig. 24. 



Section of pit working of Middlesex district. 



In the Middlesex county district, the better grades of clay 

 are generally dug by small pits. These are commonly square, 

 and about ten to fifteen feet or more on a side (Fig. 24), and 

 the depth is usually that of the thickness of the good clay in the 

 bed. Around Woodbridge the miners commonly penetrate the 

 No. 1 fire clay, or sometimes the extra sandy below, but the 

 depth is oftentimes determined by the character of the ground 

 and presence or absence of water underneath. Where there is 

 danger of the pit caving in, the sides are sometimes protected 

 in the weak parts by planking, held in place by cross timbers. 

 3 civ G 



