It is often very difficult, and sometimes impossible, to remove rust from articles made of iron. Those which are very thickly coated are most easily cleaned by being immersed in a nearly saturated solution of chloride of tin. The length of time they remain in this bath is determined by the thickness of the coating of rust. Generally from twelve to twenty-four hours is long enough. TO PROTECT IRON AND STEEL FROM RUST. The following method is but little known, although it deserves preference over many others. Add 7 oz. of quicklime to 1¾ pints of cold water. Let the mixture stand until the supernatant fluid is entirely clear. Then pour this off, and mix with it enough olive oil to form a thick cream, or rather to the consistency of melted and recongealed butter. Grease the articles of iron or steel with this compound, and then wrap them up in paper, or if this cannot be done, apply the mixture somewhat more thickly. TO KEEP MACHINERY FROM RUSTING. Take 1 oz. of camphor, dissolve it in 1 lb. of melted lard; mix with it (after removing the scum) as much fine graphite as will give it an iron colour; clean the machinery, and smear it with this mixture. After twenty-four hours rub off and clean with soft, linen cloth. This mixture will keep machinery clean for months under ordinary circumstances. FIRE-LUTE. An excellent fire-lute is made of eight parts sharp sand, two parts good clay, and one part horse-dung; mix and temper like mortar. ROPE-SPLICING. A short splice is made by unlaying the ends of two pieces of rope to a sufficient length, then interlaying them as in Fig. 48 (upper cut), draw them close and push the strands of one under the strands of the other several times as shown in the lower cut. [Illustration: FIG. 48.] This splice makes a thick lump on the rope and is only used for slings, block-straps, cables, &c. APPENDIX (_SELECTED DATA FOR MINING MEN_) TO FIND LOST PART OF VEIN Zimmermann’s rule for finding the lost part of a vein on the other side of a vein, is as follows:-- Lay down upon paper the line of strike of lode and the line of strike of the fault (cross-course), and by construction ascertain the horizontal projection of the line of their intersection; from the point where the cross-course was struck by the lode, draw a line at right angles to the strike of the former and directed to its opposite wall. Notice on which side of the line of intersection this perpendicular falls, and after cutting through the cross-course, seek the “heaved” part of the lode on that side. [Illustration: FIG. 49.]