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Moor Stone (the upper millstone of the geological survey), 
a stone much used in building, is of a coarser grain 
than the stones previously mentioned. It is composed of 
grains and rounded pebbles of translucent quartz cemented 
together with partly decomposed felspar and a little iron 
and manganese in the state of oxide. It is soft when first 
quarried, and works pretty freely, hardening when exposed to 
the air. As a building stone it is preferred, owing to its 
working much easier than the two millstones. Farbold, 
Horwich, Holcome Hill, Blackstone Edge, and Werneth 
Low are good examples of the stone. 
The upper millstone of Holcome, Bank Lane, Todmorden, 
Saddleworth, and Tintwistle is a hard and durable sandstone, 
composed chiefly of silica. It is much harder to work than 
the rough rock and stands the weather better, but it is not in 
great use, owing to its being difficult to work. 
The lower millstone, as seen at Roecross and Rhodes 
Wood, Tintwistle, and the lower part of Pendle Hill, contains 
some excellent building stones, but they are hard to w’ork and 
therefore have not been much used, but it is, no doubt, one of 
tbe strongest and most durable stones of the seiies. In the 
lower parts of it are some beds of fine grained sandstone, freer 
to work than the upper beds. A most excellent bed of this 
description is found at Bailey, near Ribchester. 
In selecting a durable building stone for a town like Man- 
chester, the more silica it contains the better. Iron or 
manganese in the state of protoxide, or sulphuret of iron as 
well as clay, all damage the stone. The stones composed of 
silica cemented with silicates of soda, potash, lime, magnesia, 
or alumina, are all durable, but when clay or salts of iron 
form the cement the acids in the atmosphere have a very 
damaging effect on the building stones containing them. 
The sandstones from the lower coal field in the neighbour- 
hood of Halifax and Huddersfield, and generally known by 
the name of Yorkshire Stone, are much used in Manchester, 
