6355. To Make Gravel Walks

6355.    To Make Gravel Walks. The bottom should be laid with lime-rubbish, large flint stones, or any other hard matter, for 8 or 10 inches, to keep weeds from growing through, and over this the gravel is to be laid 6 or 8 inches thick. This should be laid rounding up in the middle, by which means the larger stones will run off to the sides, and may be raked away; for the gravel should never be screened before it is laid on. It is a common mistake to lay these walks too round, which not only makes them uneasy to walk upon, but takes off from their apparent breadth. 1 inch in 5 feet is a sufficient proportion for the rise in the middle; so that a walk 20 feet wide should be 4 inches higher at the middle than at the edges, and so in proportion. As soon as the gravel is laid, it should be raked, and the large stones thrown back again; then the whole should be rolled both lengthwise and crosswise; and the person who draws the roller should wear shoes without heels, that he may make no holes, because holes made in a new walk are not easily remedied. The walks should always be rolled 3 or 4 times after very hard showers, which will bind them more firmly than could be accomplished by any other method.

6356. Polishing Powder for Specula

6356.    Polishing Powder for Specula. Precipitate a dilute solution of sulphate of iron by ammonia in excess; wash the precipitate, press it in a screw press till nearly dry, then expose it to heat until it appears of a dull red color in the dark. {Lord Ross.)

6357. To Make a Voltaic Pile

6357.    To Make a Voltaic Pile. Take disks of copper, zinc, and woolen cloth of any size, soak the cloth in a solution of sal-ammoniac, then pile them up in the following order: Copper, zinc, cloth, and so on. The relative position of the metals in each pair must be observed throughout the whole series, so that, if the pile commences with a copper plate, it shall terminate with a zinc one. These two extremes are called the poles. Zinc is called the positive pole, and copper the negative pole. The outer disks are connected with copper wire, that the electric or galvanic stream which is excited in the pile may be conveyed to any place desired. When the two ends of the wires are brought very near to each other, sparks are seen to dart from one to the other; this is a token of the galvanic current, manifesting itself in the same manner as the current of the electrical machine. The larger the disks and the greater their number, the greater is the intensity of the current.

6358. To Make a Cistern

6358.    To Make a Cistern. A good cistern can be made in a solid clay soil, if not in an exposed situation, by cementing against the sides of the ground. Where the ground freezes we would not recommend such a practice, but lay a wall of cobblestones in a mortar of cement, and face the wall with a thick coating of clear mortar. Great care must be exercised to get good cement, and mix it with coarse sand. Fine sand will not do at all. 1 part cement and 3 parts sand is the usual proportion, to be used as soon as mixed. Every part of the wall must be laid below the reach of the frost. This can be done, and an iron or wooden pine or throat lead to the surface, through which the pump can pass. A cheap and excellent cistern can be constructed of wood, in the form of a large cask, or a tank made of pine or cedar plank. "When sunk into the ground, and kept constantly wet, it will last for years. A better way is to place the tank or cask in one corner of the cellar, with a faucet in the bottom, from which the water is easily drawn when it is desirable to clean it out and when water is required in the cellar. An open cistern in a cellar will rarely freeze.