Inventions.

Paper Stencils.—A Frenchman has invented a way to make paper stencils by electricity. A piece of very thin paper rests on a carbon block connected with one pole of a small induction coil, while the style, with which the writing is done, is connected with the other pole. On using the apparatus a series of sparks pass between the style and the carbon block, perforating the paper, which can afterwards be used as a stencil in the ordinary way.

Combined Printing and Ruling Machine.—Paper and Press for December devotes two pages to a description, with illustrations, of a new and exceedingly accurate combined printing and ruling machine, the object of which is to secure perfect alignment of the printed matter with the ruling. The letterpress is printed from stereo plates fixed upon type-wheels, and the mechanism secures perfect correspondence between the ruling and printing. To manufacturers of diaries and blank-books this machine should be valuable.

Invisible Printing Ink.—An English firm have introduced an invisible printing ink, which becomes legible on the application of heat. They have applied for a patent, and charge a fee for the right of using the process. The ink fades out again as the paper cools, and the effect can be reproduced indefinitely. The composition is secret, but it is probably a preparation of cobalt. One of our contemporaries has issued an inset advertisement on colored paper, with specimen lines in the blank spaces. Faint yellowish-green stains are discernible either by natural or artificial light, and (the type being large) we were able, with considerable difficulty, to make out the words without applying heat. But no one would suspect their existence except for the advertisement.

Improvements in Lithography.—We notice in l'Imprimerie that M. Joseph Eberle, of Vienna, Austria, has discovered a method which is likely to transform the lithographic art, if all is true that its inventor claims, namely, that the principal advantages of the new process may be thus summarized: Drawings on stone will resist the strongest acids; the impression of crayon or pen-and-ink drawings is equal to the originals; long numbers do not affect the drawings; bad paper does not interfere with the beauty of impression; corrections can be done with the greatest facility; printing on dry paper is simplified, and it is easy to print machine, crayon and pen drawings, united in the same engravings; powdering is avoided, and in chromo work the colors preserve a sharpness of tone hitherto unattained.—American Lithographer and Printer.

Can for Printers' Ink.—The following is a description of an improved can for printers' ink, invented by Mr Charles H. Hollis, of Boston, Massachussets. The head of the can is integral with the body, an egress for the ink being provided by a nipple, which is situated in the centre of the can head, and may be closed by a screw-cap. A movable bottom—described in the specification as a « concavo-convex follower » —is adapted to slide longitudinally within the body of the can, and is surrounded by annular packing which prevents leakage without restriction of motion. If the screw-cap be removed and the bottom of the can pressed in, the ink will be forced from the nipple in the same manner that paints are exuded from the collapsible tubes which contain them. This can possesses the two principal virtues of collapsible tubes: the manner of ejecting its contents, and the protection it affords its contents against dust. It differs from collapsible tubes in that, owing to its rigidity, it preserves its form, and may be refilled when empty.

Relief Gold Printing.—The following method of printing gold in a high relief upon satin, silk ribbon, &c, has been patented in Austria, by Philip Klopper, of Augsburg:—For this kind of printing the inventor engraves a brass plate with the necessary design in the same manner as is usually done by an embossing plate. This plate is now filled up with a well-mixed fluid of 7 parts of (so-called) gold oil and 15 parts concentrated sulphuric acid; then it is given a coat of brocade or gold bronze, leaving room for a binding medium, consisting of 12oz. of the finest glue, which is dissolved in 3 pints of water at a temperature of 190° to 200° F. to which a portion of 12oz. of white chalk is added. The plate now is so entirely filled up that it is levelled by a straight-edge of brass, rubber, &c., and all superfluous substances removed; for perfect cleaning a woollen rag or cloth may be used. The silk ribbon, or other material, is now placed surface-down upon the plate, which has been warmed with alcohol, or by any other method of heating, to about 122° F. and then an impression is made in a regular copying-press, a thick rubber blanket having been first placed on top of the silk. After a pressure of about ten minutes the impression is taken off, and the design appears in a very brilliant relief. The warming of the plate is done to secure a quicker drying of the composition.