(19) W. A.—To clean marble from discoloration: Try 2 parts sodium carbonate, 1 of pumice stone, and 1 of finely powdered chalk. Mix into a fine paste with water. Rub this over the marble, and the stains will be removed; then wash with soap and water.
(20) F. B. asks in regard to papier mache floor covering: 1. Will it hurt to use printed paper? A. According to the article “A Papier Mache Floor Covering” we find Manila paper recommended. It is very likely that newspaper would answer, but it is by no means as strong an article as the variety spoken of. 2. How thick will that covering be? A. The thickness depends upon whether more than a single thickness of the paper is used—probably from one‐sixteenth to one‐eighth of an inch in thickness. 3. How long will it be before it is ready for use? A. That depends entirely upon the drying; if artificial heat is applied, we should think that the whole operation could be carried through and the covering finished within a week.
(21) C. C. C. asks: Which would be the best test for water works—to have three streams on one main near each other, or three streams on different mains scattered over the town? The mains 8 inches, 6 inches, and 4 inches, works half a mile from town. A. If you are testing in the interest of contractors, place the trial streams as near the source of supply as possible, and also near the 8 inch main. A fair test will be to locate the streams widely apart on one distributing branch.
(22) F. L. asks how to imitate walnut graining. A. Try the following: The wood, previously thoroughly dried and warmed, is coated once or twice with a stain composed of 1 ounce extract of walnut peel dissolved in 6 ounces of soft water by heating it to boiling, and stirring. The wood, thus treated, when half dry is brushed with a solution of 1 ounce potassium bichromate in 5 ounces boiling water, and is then allowed to dry thoroughly, and is to be rubbed and polished as usual.
(23) Z. T. D. asks: How much water per second will flow through a 14 inch pipe, 80 feet long, with 8 feet head? Also, 18 inch and 21 inch pipes, same conditions? A. The discharge for 14 inch pipe, 18 cubic feet per second. For 18 inch pipe, 34 cubic feet per second. For 21 inch pipe, 50 cubic feet per second.
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PATENTS.
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