(From the Pacific Printer.)

Elastic Mucilage.—To twenty parts of alcohol add one part of salicylic acid, three parts of soft soap, and three parts of glycerine. Shake well, and then add a mucilage made of ninety-three parts of gum arabic and one-hundred-and-eighty parts of water. This is said to keep well, and to be thoroughly elastic.

To Preserve Pencil Writing.—To preserve marks of the ordinary lead pencil, two plans are proposed: (1) Coat them over with a solution of collodion, adding two per cent. of stearine; (2) Immerse the paper containing marks in a bath of clear water, then flow or immerse in milk a moment, and hang up to dry.

To give Ink a Metallic Hue.—To give printer's dark ink a bronze or changeable hue, take one and one-half pounds of gum shellac and dissolve it in one gallon of ninety-five per cent. alcohol spirits of cologne for twenty-four hours; then add fourteen ounces aniline red; let it stand a few hours longer, when it will be ready for use. Add this to good blue-black or other dark inks, as needed, in quantities to suit, when, if carefully done, they will be found to have a rich dark or changeable hue.

(From the British and Colonial Printer and Stationer.)

Photographs on Leather.—A successful mode of taking photographs on leather has been patented by Herr Lewisohn, of Stuttgart. A coating of copal varnish is put upon the leather, and well dried; then a second coating is placed over it, composed of albumen and white lead. When this is dry the faced leather is ready for the silver bath, which forms the sensitive surface. The composition of the albumen and white lead varnish need not be very definite, so long as the stratum of lead deposited is thin and uniform. A little practical experience soon enables the operator to estimate the proportions to a nicety.

Olive Oil for Litho Rollers.—A lithographic printer, a practical man, writing in the Gutenberg Journal, states that, instead of preparing a new roller with strong varnish and block, as is done by many printers in France, he applies olive oil, rolling up in it until the leather, the flannel, and even the wood have imbibed as much as can be got into them; the surface is then scraped, and mordant and finally black applied. Scraping is done with a sharp knife in oblique streaks, first one way and then the opposite. The writer states that he has had in use for twenty-five years a roller prepared in this manner.

(From the Scientific American.)

Slipping of Leather Belts.—The slipping of belts is a great annoyance, not always remedied by tightening. The writer has known a slipping belt to be so shortened as to spring the shaft without preventing the slipping. The radical remedy is to keep the belt pliable, so as to hug the faces of the pulleys; but this is not always feasible. The belt may be softened by neatsfoot oil or by castor oil. A siccative oil, like linseed oil, is unfit for a leather belt, as it has an affinity for the oxygen of the atmosphere and reverts to its acid base, which is injurious to the leather. When a ready remedy is demanded for a slipping belt, the powder known as whiting, sprinkled sparingly on the inside of the belt, is least harmful of any similar application. Powdered resin is bad, as it soon dries the leather and cracks the belt, while it is difficult to get it out of the leather; whereas whiting may be wiped off or washed out with water. The use of water on belts, preliminary to oiling, is good. The belt should be washed on shutting down at night, or Saturday, after the close of work, is better, and then the oil applied when the belt is partially dry. Never oil or wash a belt while stretched on the pulleys. If iron-faced pulleys were always lagged with leather, there would be little complaint of the slipping of belts. But often this slipping is due to too much strain on the belt; there is economy in running wide belts, wider than is the usual practice. Many a 3-ineh belt has to duty for a 4-inch belt, to the annoyance of the operator and the ruin of the belt.