Rensselaer Republican, Volume 17, Number 35, Rensselaer, Jasper County, 7 May 1885 — MECHANICAL. [ARTICLE]

MECHANICAL.

The pearls of . commerce, found in the mantle of some mollusks, are similar in structure to the shell; but what is the innermost layer in the shell is placed on the outside, of the pearl and is much finer and more compact. The pearl is formed around some nucleus, as an organic particle or grain of sand. To ctEAN marble mix powdered chalk and powdered pumice stone, each one part, with two parts carbonate of soda into a paste with water, and rub it thoroughly pn the marble, or mix quick-lime and strong soap lye to 1 the consistency of milk, and apply it to themarble for twenty-four hours. In either case wash off thoroughly with soap and water. * Dr. Klezko, of Vienna, has suggested the use of petroleum or paraffine as a powerful preventive of cholera. In that portion of the eastern country where petroleum oils are found, the working people have so far escaped completely from cholera, even when it has broken out in the districts immediately around them. Thia is attributed to the emanations from the petroleum producing soil, which are supposed to kill the pestilential germ as well as all kinds of insects. The Society of Chemical Industry published in their journal this process for nickelplating zine: The zinc, having been cleaned by means of dilu’e hydrochloric acid and thoroughly washed, is hung in the nickel bath for a short time, and when it is taken out it is rinsed and scraped, so as to remove all the coating that does not adhere firmly. This is repeated until the zinc,is covered with a thin Aim of nickel, which can afterward be made as thick as desired. The suitable current strength is easily found. When the zine is onee thoroughly covered the current may be increased without incurring any risk of peeling off. A new kind of slate roofing has come into favor. Each slate is laid in a peculiar kind of cement, consisting of liquid coal tar thickened with a eOment, or, better still, a quantity of ground slate, slaked lime, and linseed oil, the proportions varying according tb the requirements of the case. This substance is heated until liquid, poured on a shed roof, and the slates embedded in it with their whole face exposed. When of just the right thickness, the compound adheres with extreme tenacity to the slate, and cannot be detached without violence. The cost of a roof of this kind is said to be less than one of tin, and, qn account of the greater surface exposed, is considerably cheaper than ordinary Slate roofs. A fish found no where else in the world is the golden trout es Kern Biver, California. Its flesh is hard and sweet, but it is noted particularly for the beautiful color which flakes its sides, looking as though they had submitted to a coating of gold foil. The Inyo Independent says : “This peculiarity of color and their distinct species are preserved by a natural barrier existing between them and the other varieties which are found m this creek. A series of high land rocky falls prevents other fish from ascending and mingling with them, and so, from generation to generation, they have, by a natural barrier, been able to preserve their distinct character. At times some of them have descended into the lower course of the stream, and a mixed tribe of trout, combining the speckled and the golden trout, has been found, individuals of which are often caught”