BUILDING STONE. 587 
tion is also variable. That which is of medium hardness and of uniform 
texture is used for building purposes or for grindstones ; some is too 
hard or not sufficiently uniform in texture for grindstones, and is used 
_ for building purposes only ; and the material sometimes found which is 
difficult to quarry and to dress is used for bridge-building purposes only. 
As regards appearances there is much diversity in the material pro- 
duced in this region. There are differences due to diversity of textures, 
of colors, and of methods of stratification, yet these are seldom recog- 
nized by the casual observer. Differences in color give rise to the 
terms ‘blue’ and “buff” previously referred to, and differences in 
methods of stratification give rise to the terms “ split-rock”’, ‘ spider- 
web”, and “‘liver-rock”. The regularly and evenly stratified stone 
is classified as split-rock ; that in which the stratification is irregular 
and marked by fine, transverse, and wavy lines is classified as 
spider-web; the homogeneous stone which exhibits little or no strat- 
ification is classified as liver-rock. ‘These lines of stratification are 
frequently marked by the presence of black ingredients which are 
composed of mica and carbonaceous matter. As regards composition, 
these stones are mainly a siliceous sand ; and analyses show that the dry 
material contains usually as much as 96 per cent. of silica, with a small 
amount of lime, magnesia, iron oxides, alumina, and alkalies. When 
first taken from the quarry it contains several per cent. of water, and as 
long as this is retained the stones cut easily ; upon its loss they harden. 
Analyses made for the Clough and Columbia Stone Companies show 
that their stones contained respectively 5.83 per cent. and 7.75 per 
cent. of water when wet, and 3.39 and 4.28 per cent. of water when 
dry. The stone is extracted during only eight months of the year, 
since it is injured by being quarried in the winter and subjected to hard 
freezing while still containing this quarry water. The winter months 
are, therefore, occupied in stripping and channeling. The average 
thickness of this sandstone formation is more than 60 feet in these 
counties, and in many places, as, for instance, at the Brownhelm quarry, 
it is over 80 feet in thickness. An acre covered by stone only 50 feet 
in thickness would furnish over 2,000,000 cubic feet. Many very fine 
buildings, both in the United States and Canada, have been built of the 
so-called Amherst stone, among which may be mentioned the Canadian 
Parliament buildings, and most of the public buildings in Toronto; and 
there is no city in the Union in which stone is extensively used where 
