SCIENCE AND ART.

New Zealand Herald, Volume XXIII, Issue 7662, 12 June 1886, Page 6 (Supplement)

SCIENCE AND ART.

To frost brass work and give it ornamental finish, boil the article in caustic potash, rinse in clean water, and dip in nitric acid till all oxide is removed ; then wash quickly dry in boxwood sawdust, and lacquer while warm. From tests made by Dr. Fisher, the German chemist, it appears that in ordinary stoves not more than 20 per cent, of the fuel consumed is utilised, whereas with gas burning stoves SO per cent, of the possible effect is obtained. Spiders have been found by Dr. C. Keller, Oi Zurioh, to be voracious destroyers of plant-preying insects, and he contends that they play a more effective part in the preservation of forests than all the insect-eating birds together. Platinum wire can be drawn so fine that it is no longer visible to the "naked" eye, and can only be felt. It can be seen with a magnifying glass, when the wire is held against white paper. It is used in telescopes and similar instruments. To find capacity of a cylindrical vessel in gallons, multiply the area in inches by height in inches, and divide product by 231. To find capacity of a four-sided vessel in gallons, find cubical contents by multiplying the length, breadth, and height in inches, and divide product by 231. Professor J&tclam, the German hygienist, declares that night air is injurious only in swampy regions, whereas on dry soil, in the mountains, and everywhere in the upper stories of the house, it is more salubrious than day air. Neither does he consider draughts hurtful unless one is in a glow. A mixture of,cork, silica, and lime is coming into extensive use in Germany as a building material. It has the advantage of keeping out heat and cold, and is also claimed to be an excellent preventive of damp and defender of sound. It is substantial, light, and durable, and seems especially adapted for ceiling and wall lining. An automatic railway gate has been patented by Mr. James K. Patterson, of Crete, Neb. It has main bars pivoted to a side post, and pickets hinged to the bars, so that as the gate is lifted vertically by the weight of an approaching train, the pickets will hang down somewhat as a fan closes, aud after the train has passed the gate will come down in place mainly by its own gravity.

A novel uie i« now made of the stereoscope to detect forged bank, notes. A note of £4 'was recently submitted to the experts of the Bank of France an issued by a band of forgers, but the execution was so perfect that no defect could be discovered by the closest examination. A suggestion was then made to place the suspected note side by side with a genuine one in the objective of a stereoscope, the two images of which, as well known, overlay each other and form a single picture. The result of the experiment was that the loop of a letter of the forged did not xactly cover that of the genuine one, Bhowig that they had not been printed from the xme plate. The extension of the telephone is one of the most remarkable in the history of inventions. In August, 1877, the instruments in use in the United Stateß were only 788. while in February, 1885, there were 325,574 There are about 18,000 in Canada, and 13,000 in Great Britain. The number of exchanges has grown in America from 100 in 1880, to 782 in 1885. In January last there were 137,223 miles of telephone wire in that country. There are 5186 persons employed in the American telephone exchanges. More patents have been issued on the telephone than in any other single line of invention in the United States. The total cumber for the last ten years is 1521. An important invention in connection with the use of the pianoforte has been patented by Metiers. Marsden and Wright, dealers in musical instruments, JHunslet Lane, Leeds. It is a "hand guide," in which great improvement is made upon similar inventions. It consists of a bar of polished American walnut, which, by an ingenious arrangement, can be fixed by anyone to any kind of piano. A correct position of the hand in playing is of the utmost importance, and this the use of the guide is intended to givei The inventors claim for it that, under th'i supervision of a competent teacher, " the learner will be taught to play in a correct manner from the commencement, ... able to practice a much longer time than before, and with less fatigue, and it will be found to be equally beneficial in legato or staccato exercises." These claims are supported by the unqualified testimony of eminent players and teavhers,