426 
Cast Steel. 
the old pavement of the streets of London, which is the 
best material yet known for finishing a fine edge. 
The grindstone leaves a ragged edge, which it is the 
first effect of whetting to reduce so thin, that it may be 
bended backwards and forwards. This flexible part is 
called the wire, and if the whetting were to be continued 
too long, it would break off in pieces without regularity, 
leaving a finer, though still very imperfect edge, and tend- 
ing to produce accidents while lying on the face of the 
stone. The wire is taken off by raising the face of the 
knife to an angle of abut 50 degrees with the surface of the 
stone, and giving a light stroke edge foremost alternately 
towards each end of the stone. These strokes produce 
an edge, the faces of which are inclined to each other in an 
angle of about 100 degrees, and to which the wire is so 
slightly adherent, that it may often be taken away entire, 
and is easily removed, by lightly drawing the edge along 
the finger nail. The edge thus cleared is generally very 
even : but it is too thick, and must again be reduced by 
whetting. A finer wire is by this means produced, which 
will require to be again taken off, if for want of judg- 
ment, or delicacy of hand, the artist should have carried 
it too far. But we will suppose the obtuse edge to be 
very even, and the second wire to be scarcely perceptible. 
In this case the last edge will be very acute, but neither 
so even nor so strong as to be durably useful. 
The finish is given by two or more alternate light 
strokes with the edge slanting foremost, and the blade of 
the knife raised, so that its plane forms an angle of about 
28 degrees with the face of the stone. This is the angle 
which by careful observation and measurement, I find Mr. 
Stodart habitually uses for the finest surgeons instruments, 
and which he considers as the best for razors, and other 
keen cutting tools. The angle of edge is therefore about 
56 degrees. 
