TABLE, Showing what Weight a Hemp Rope will bear with Safety. The size of a rope is designated by the circumference, measured with a thread; thus, a 3-inch rope measures 3 inches round. The utmost strength of a good hemp rope is 6'400 lbs. to the square inch; the weight it will bear before breaking is expressed in tons by of the square of the girth, in inches. In practice, a rope should not be subjected to more than half this strain; it stretches from to, and its diameter is diminished from to, before breaking. A difference in the quality of hemp may produce a difference of in the strength of ropes of the same size. 12 The strength of Manilla is about that of hemp. White ropes are more durable. The best quality of hemp is of a pearl gray; the next, greenish; then the yellow. A brown color indicates decay; the odor should be strong, and free from mustiness. To find the Strength of Ropes. Rule. Multiply the square of the circumference by 200, the product will be the weight, in pounds, the rope will bear with safety. PAINTS, LACKERS, &c.* COMPOSITION AND PREPARATION. The proportions are given for 100 parts, by weight of prepared colors, &c., when not otherwise designated. NOTE. A gallon of linseed oil, New York measure, weighs 7:45 lbs.; of spirits turpentine, 7 lbs. Put the copperas and litharge in a cloth bag, and suspend it in the middle of the kettle. Boil the oil 4 hours, with a slow, even fire, so that it may not be burnt; then let it stand, and deposit the sediment. DRYINGS. Mixture of copperas and litharge, taken from the boiled oil 60 56 2 The mixture taken from the boiled oil to be ground, and mixed with the turpentine and oil. Made into a stiff paste. If not intended for immediate use, raw oil should be used, as the putty made with boiled oil hardens quickly. Grind the white lead in the oil, and add the spirits of turpentine. New wood-work requires about 1 lb. to the square yard, for 3 coats. The lampblack and the litharge are ground separately upon the stone, in oil, then stirred into the white lead and oil; the turpentine and varnish are added as the paint is required for use, or when it is packed in kegs for transportation. 1 square yard of new brick-work requires, for 2 coats, 11 lb. ; for 3 coats, 1.5 lb. 1 square yard of new brick-work requires for 1st coat, 0.75: for 2d coat, 0.3 lbs. Dissolve the beeswax in the spirits of turpentine, with a gentle heat, and mix the paint warm. 2. Add 12 oz. of beeswax to 1 gallon of linseed oil, and boil it two hours; prime the cloth with this mixture, and use the same. in place of boiled oil, for mixing the paint. Give two coats of paint. Boil it gently about twenty minutes, during which time it must be constantly stirred. All the ingredients should be pure, and of the best quality. Heat them together in a copper or earthen vessel, over a gentle fire, in a water bath, until they are well mixed. Add the litharge to the oil; let it simmer over a slow fire 3 hours; strain it, and add the rosin and white lead; keep it gently warmed, and stir it until the rosin is dissolved. Apply it with a paint brush. The solid shot broke against the granite, but not against the freestone or brick. The shells broke into small fragments against each of the three materials. Ordnance Manual. EXPERIMENT IN NEW-YORK HARBOR, IN 1814. Penetration in a Target of White Oak Timber, 5 feet thick. 2.10 1.80 1.43 0.94 0.65 0.29 0.00ft Indentation 0.2 inches The musket fired at 9 yards distance, with a charge of 134 grains, 1 ball and 3 buckshot, gave for the ball a penetration of 1·15 inches; buckshot, 0.41 inches. |