WORKING OLAY 



147 



vertical face, and as a result the bank slid, burying the shovel. 

 Where the clay bank contains several different layers of clay, 

 which are mixed together for making brick, the steam shovel is 

 a good thing, as it digs from bottom to top of the bank each 

 time. 



5. Dredging. — This method like the preceding is only prac- 

 tised at one locality, viz., Croton Point. The dredged clay is 

 dropped into hoppers, which, when full, are run up inclined 

 planes on shore and dumped. Costs 12- 1 5c. per 1000 delivered 

 on shore; then 12c. for haulage to ring pits. 



6. Undermining. — Many brick manufacturers use this method 

 of mining their clay, especially when the latter is tough. 

 Wedges are driven in on the upper surface a foot or two from 

 the edge ; at the same time the face is undermined by picking to 

 a distance of two or three feet. It is not advisable to work a 



Shale bank covered by a shed. 



bank over 20 feet high by this means, and in almost any case it 

 is a rather dangerous method to employ. 



7. Blasting is very often resorted to in banks of tough clay 

 and always in the case of a shale bank. A small charge of 

 dynamite usually suffices to bring down a large quantity of the 

 material. 



