Rensselaer Union, Volume 7, Number 41, Rensselaer, Jasper County, 1 July 1875 — MECHANICAL AND SCIENTIFIC. [ARTICLE]

MECHANICAL AND SCIENTIFIC.

—Awnings can be rendered waterproof by plunging the fabric into a solution containing 20 per cent, of soap and afterward , into another solution containing the same percentage of sulphate of copper. Wash, and the operation is finished. —To make a cheap galvanic battery take a cylindrical vessel, and put another of porous porcelain inside of it; fill the vessel with diluted sulphuric acid, and the space between the two with sulphate of copper (if you require to plate the article with copper); if not a solution with the salt of gold, silver, etc., according to that which you wish it to be; put a slip of zinc in the sulphuric acid and attach a copper wire to it, and the other end to the medal or article you wish to plate, and immerse that in t.lie other solution. Your battery is now complete. If you want the copper to be very thick you must put a few solid crystals of copper in the solution ; where you do not want it to come in contact you must touch it with a little grease; if you want to take the copper off the article you must do it over with a slight varnish. —Of late years one of the most important and useful operations in surgery has been that of grafting new and healthy skin upon a wound or sore and thus establishing the healing process and obtaining a cicatrization. Hitherto the particles of skin have been taken from some sound part of the patient’s body and applied to the diseased or injured point, but M. Anger lias recently demonstrated that pieces of skin may be taken from amputated limbs and used successfully in heteroplasty. In one case M. Anger took strips of skin from the palmer surface of an amputated finger and applied them to the ulcerated leg of another person. In three days the bandages were ' removed and the grafted parts found firmly united to the surface and evidently vascularized. To insure success it is necessary that the graft be made immediately upon amputation.

—An ingenious apparatus for sawing wood has been introduced in England with very* satisfactory results. In order to secure the log from rising with the drag of the saw on its bed while being cut it is kept down by means of pressing rollers or bowles, carried by vertical water cylinders, in which stationary pistons are inserted, their rods being pendant from a transverse beam of the saw frame. The upper and lower ends of each cylinder are brought into communication by an outside pipe which allows the water which fills the cylinder to pass from one to the other side of the fixed piston. The water forms an elastic packing between the piston and the lower ends- of the cylinder and serves to retain the bowles of the cylinders in contact with the timber when once lowered in contact therewith. In order that the machine may operate upon balks or logs of varying thickness the cylinders are fitted with a vertical rack in gear with pinions for raising and lowering the cylinders.

—lt is stated that previous to its being made known that Mr. Lick, of San Francisco, intended to found an observatory witli the grandest telescope in the world a similar instrument had been projected in France by M. Foucault, in ISGS, but. was ;suspended in consequence of the latter's death. It has since, however, been resumed under the direction of M. Wolf, and the work is being pushed forward as rapidly as possible. The tube of this gigantic instrument is nearly fifty feet long and six feet eight inches in diameter, The reflector is to be produced at the St. Gobin glass works, and the production of the mold alone, which is already completed, occupied six months. The mirror w ill be produced spherical and will afterward be worked up to a parabolic form, and will finally be covered with silver or gold. The power of this telescope will be far greater than that of any other hitherto constructed —to be greatly exceeded, however, by the Lick instrument. The Atlantic cotton mills, of Laurence, Mass., employing 1,250 operatives, and manufacturing 450,000 yards per week, will shut doWrn on account of the dull market on the 10th of July, and remain closed till Sept. 1.