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(1) G. W. B. asks: 1. What kind of cement used, and how to cement gum face on band saws? A. Ordinary rubber cement, such as you can purchase at any of the rubber stores, will answer your purpose. 2. Is there anything to be put in glue to prevent moisture from disturbing the joints in patterns? A. A little bichromate of potash put into your glue will render it insoluble, after exposure to light. 3. Is there anything to prevent shellac used for patterns from getting dark before using after it is mixed some time? A. We know of no way to prevent this.
(2) W. S. C.—In closed circuits for steam heating, the pressure of the steam along the flow pipes and in coils in well arranged systems is so nearly equalized with the pressure in the boiler, that it requires but small elevation of the water of condensation in the return pipe above the water level in the boiler to allow of its return by gravity. In this system all of the radiators should be not less than from 1 to 5 feet above the water level in the boiler, according to the complication and extent of the circuit. The air is discharged at the radiators, and no waste of water is necessary.
(3) E. H. S.—Coal tar alone with gravel and sand for sidewalks does not dry well. Asphaltum with equal parts of coal tar melted together and sprinkled upon the mixed sand and gravel that has been made hot upon an iron plate (the mixing to be done in a large pan of iron), putting no more asphalt and tar upon the sand and gravel than will just make it stick together; then dump into place while hot, spread quickly, and beat level with a ram or heavy roller. Dust over the surface with fine sand before rolling or beating, to prevent the material from sticking to the roller or beater. This operation requires a little care and experience as to just the amount of asphalt and tar for a given measure of sand and gravel, and also for the proportions of sand and gravel required to make the best pavement. Sometimes a thin bed of broken stone is laid as a foundation. Also a thin bed of coarse gravel is sometimes spread before dumping the hot mixture.
(4) J. C.—A first class ice boat, sailing on first class ice, will sail from three to four times faster than the wind that drives the boat. For example, a wind having a velocity of fifteen miles an hour will drive the boat at the rate of from forty to sixty miles an hour.
(5) T. H. G. writes: I have a mahogany table which has been varnished and has ink spots on it. 1. By what means can I get the varnish and ink off, in order to rub on an oil finish? A. The ink spots can be washed off with water and the varnish with alcohol. 2. What is best to polish carved brass? A. Polish with rotten stone and oil, alcohol, or spirits of turpentine. 3. What will remove water stains from polished marble? A. Mix quicklime with strong lye,
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