67 
PEBBLES. 
In the grinding of materials a certain type of machine 
is sometimes used, known as a pebble mill. The material to be 
pulverized is charged into the cylinder, which is rotated. The 
constant shifting of the pebbles contained grinds the material 
to a high degree of fineness. This type of mill is extensively 
used in the grinding of cement. 
The pebbles used should be tough, hard, and not easily 
split or chipped. 
Well rounded pebbles of flint, quartzite, and granite, measur 
ing about four inches in diameter, are those usually used for the 
grinding of cement clinker. 
The price varies from $8 to $12 per ton. 
Amount of pebbles used in the manufacturing industries, 
as reported by the consumers:— 
Location 
No. of firms 
reporting 
consumption 
Domestic and Imported 
Tons 
Maritime Provinces 
Quebec 
1 
725 
Ontario 
11 
1030 
Prairie Provinces 
3 
270 
British Columbia 
1 
200 
Canada (Total) 
16 
2225