22 
of large gang-saws. The industry continued to flourish and for 
several years no stone was cut excepting the Labrador oilstone, 
but after three years other kinds were also received until to-day 
there are over two dozen varieties of whetstone handled at the 
factory. 
STRUCTURE OF THE STONE. While almost everybody is 
sufficiently acquainted with whetstones to know their most 1m- 
portant uses and qualities, only a few know what to expect of a 
stone or how to care for one after it is obtained. Because the 
whole subject seems so simple and so common it is given little, if 
any, thought even by persons who constantly use whetstones, and 
they are the losers thereby. Many a valuable stone has been 
ruined by being used just once by the person who knows nothing 
about the proper care of a stone and who thinks there is nothing 
to know. 
The Labrador stone has been described by Griswold as a 
hard tough sandstone of keen grit, particularly suitable for glass- 
worker’s and carver’s files. 
There are at least three factors which determine the effec- 
tiveness of every whetstone: the size of the grit grain, its form 
and composition, and its structure. 
Looking at these three qualities in the order mentioned we 
find (1) that the effectiveness of a stone will depend on its ability 
to scratch off particles of the substance which is being sharpened. 
Some one has said that the grains may be likened to sharp teeth, 
which are comparatively large, in coarse gritted stones, and small 
in those of finer grit. In the coarser varieties the spaces between 
the cutting points are so large that the scratches made on the tool 
are far apart, deep scratches are also made by these large points, 
and hence because the furrows are both deep and far apart it is 
impossible to obtain a fine edge with a coarse stone. The fine 
grained stones on the other hand show only small particles of 
grit crowded closely together, so closely in fact that each grain 
makes only a tiny scratch, while the furrows are so close together 
that the eye cannot distinguish the individual scratches and the 
result is a polished surface. These little grains cannot work rap- 
idly and the amount of work given them to do should not be 
