_Hardening._--The pen is now too soft, and is hardened by heating and the immersing in oil while hot, after which it is thoroughly cleansed from all grease. _Tempering._--The pens are now hard but very brittle, and in order to correct this defect they are placed in an iron cylinder, and kept revolving over a gas or charcoal fire until they acquire a proper temper. _Scouring._--After soaking in diluted sulphuric acid, the pens are placed in iron cylinders containing fine stone and water, or fine sand, and revolved for several hours. When taken from these cylinders they are bright and smooth. _Grinding._--This is a process performed by hand on a “bob,” or wooden wheel covered with leather and dressed with emory, revolving at high speed. A light touch on the emory wheel grinds off the surface between the pierce hole and the point, to obtain proper action and to assist the flow of ink. _Slitting._--This is a hand process performed with a press, the cutters being as sharp as razors. The pen is placed in position by means of guides, and must be cut with utmost precision from the pierce hole to the point, the point must be divided exactly in the middle, the least variation making the pen defective. _Coloring and Varnishing._--The pens having been polished to a bright silver color are placed in an iron cylinder and kept revolving over a gas or charcoal fire until the tint required is produced. They are then immersed in a bath of shellac varnish, and afterwards dried in an oven. _Examination._--Every steel pen passing through the factory is most carefully examined before being boxed, and should the least fault be found, it is at once rejected.] Why Does a Pencil Write? You can use a pencil to write with or to make marks, because the pencil wears off if you are scratching it on a surface that is rough enough to make it do so. Writing, you know, is only a way of making marks in such a manner as to make them mean something. You cannot write with a pencil on a pane of glass, because the glass is so smooth that when you move the pencil over its surface, the pencil will not wear off. To prove to yourself that the tip of the pencil constantly wears off when you write, you have only to recall that when you write with it a pencil keeps getting shorter and shorter. A slate-pencil will wear down short by merely writing with it, but a lead-pencil must be sharpened--that is, you must keep cutting away the wood in order to get at the lead inside. Why Can’t I Write on Paper With a Slate-pencil?