Tools of Stone Ware . 387 
NO. 77. 
Tools to answer the Purpose of Files and other Instru- 
ments, for various Uses , made of Stone-ware. By G, 
Cumberland, Esquire. 
SIR — To some men, but not to you, will it appear a 
trifle, because very obvious on reflection, to have applied 
so soft a substance as clay to the purpose of lograting 
tbe hardest bodies ; neither should 1 perhaps have ever 
thought of such an application in the form I now use it, 
had I not found, in shaping of some substances, that the 
wear of my steel flies was rather expensive. 
It then first occurred to me, in ranging in thought after 
a remedy, that, as our stone-ware is so hard as to blunt 
our files, files might be as well made ol our stone ware. 
This was about two years ago, and the first use I made 
of this suggestion was, to fold up in muslin, cambrick, 
and Irish linen, separate pieces of wet clay, forcing them 
by the pressure of the hand into the interstices of the 
threads, so as on divesting them of the covering to re- 
ceive a correct mould. These I had well baked, and 
immediately found I had procured an intire new species 
of file, capable even of destroying steel ; and very useful 
indeed in cutting glass, polishing, and rasping wood, 
ivory, and all sorts of metals. 
The ease with which I had accomplished my purpose, 
as is too often the case, made me content myself with 
the use of my own discovery, or at most giving away a 
few specimens as files for ladies nails of peculiar delica- 
cy : but having since reflected, that in glass grinding (the 
stones for which come from the North, and are very ex- 
pensive) in flatting metallic mirrors, laying mezzotinto 
* Nicholson, vol. 25, p. 257. 
