Files and Sand-papers.
HAVING now examined the analogies between the cutting, boring, striking and grasping tools of Nature and Art, we come to those finishing tools which smooth and polish the surface.
The first is the File, an instrument which needs but little description. It consists of a surface of hardened steel, broken up into rough-edged teeth of infinite variety, according to the work which the file has to do. It is rather remarkable, by the way, that at present the English files are infinitely superior to those produced in any other part of the world; that their teeth are all made by hand; and that a genuine Sheffield file will first cut its way through a piece of iron in half the time that would be occupied by a file of any other nation, and then would easily cut its antagonist in two.
As long as the File is intended to work upon metal, there is little difficulty in its manufacture, except that no machinery has yet been invented which can give the peculiar edging of the ridges, and to which is owing the unmistakable “bite” of a real English file.
But there are occasions when the hand of the most cunning file-maker is baffled, and when it is necessary to cut files so delicate that the unaided human eye cannot trace their teeth. Art, therefore, has recourse to Nature, and the cabinet-maker, who cannot obtain any file made by human hands which will answer his purpose in the higher branches of his trade, makes great use of the “Dutch Rush,” as he calls it. It is not a rush at all, but simply a species of Mare’s Tail, or Equisetum, a plant which fills in profusion almost every marshy spot in England.
The peculiar fitness of the Equisetum for this purpose cannot be appreciated even by those who use it until it has been viewed under the microscope. I have now before me a small piece of Equisetum, placed under a half-inch power, and viewed by direct illumination, it being treated as an opaque object.
The microscope reveals at a glance the source of the power which the ingenuity of man has taken advantage of. The surface of the Equisetum is seen to be composed of myriads of tiny parallel ridges, each ridge bristling with rows of flinty spicules, looking very much like the broken glass upon the top of a wall. Minute as they are, these spicules can do their work, and they enable the joiner to finish off work in a manner that could not be accomplished by any tool made by human hands.
I find, by recent inquiries, that modern joiners scarcely, if ever, use the Equisetum, preferring emery-paper as cheaper and more expeditious, and knowing that the popular eye is not able to appreciate the difference of the surface obtained by the Equisetum from that which is given by the finest emery-paper ever made. Wood-carvers, however, if they be of the conscientious kind, and love their work for its own sake, adhere to the Dutch Rush, and are all the happier for it.
Pass we now to the coarser kinds of polishers, the chief of which is popularly known as Sand-paper, and is made by coating some tissue with glue, and scattering upon it sand of different qualities, according to the work to be done. Sometimes, when the work is rough, the sand is large, rough, and coarse, and sometimes, when the work is fine, the sand is so carefully sifted before it is scattered on the glued paper, that there is little distinction between the sand-paper and emery-paper. Linen, by the way, is generally used instead of paper, as being more enduring, less liable to crack, and capable of being folded so as to obtain access to crevices which paper could not touch.