NOTES ON SCIENCE, MECHANICAL INVENTIONS, ETC.

New Zealand Herald, Volume XXVIII, Issue 8580, 30 May 1891, Page 4 (Supplement)

NOTES ON SCIENCE, MECHANICAL INVENTIONS, ETC.

1 INTERIOR TEMPERATURE'OF TIIE EARTH. It is common to assume tihat the temperature of the earth'' toward the centre increases one degree for/every 60 feet in depth. This, however,/is far from being universally ! the case. It does not hold good in California, norfin the Sierra Nevada Mountains. At . Virginia, Nevada, in the Conisbock mines, the .'temperature in some cases increased one degree for each 20 feet up to 1000 feet in depth, or for 2500 feet one degree for each 30 •o feet—twice as fast as the rule first named. • i At Manchester,; England, in ajshaft 2500 feet deep, the temperature is only ,75 degrees. In a copper .;■ mine L at Cornwall, 2100 feet deep, l the temperature is 88 degrees* Substracting 42 degrees for the surface temperature, this makes in the first case a change of one degree in 65 feet, and in : the j second one degree, in 46*6 feet, from which it may be inferred there is no, uniformity in the matter, consequently no rule. MOULDING SAND : WHAT IT SHOULD 8E.."; In a recent number of Ferdinand Kohn's Iron and Steel Manufacturer is given the following valuable information in regard to moulding sand, which will be of value to many readers who have often wondered, no doubt, why castings mode in different localities from the same iron should differ so much :—" The mould has an important function to perform in the process of casting. It must resist the pressure of liquid metal in every direction, and at the same time give a freo escape to the air and gases generated in the mould while being filled and during solidification. It must give to the casting a clean, smooth surface and allow an easy separation from the sand. ■ It must neither act chemically upon the liquid, metal, nor be affected by it at the high temperature at which it is brought in contact with the sand. The higher the temperature of the liquid metal, the more difficult it is to comply with these conditions, and the fewer are the substances which can be used for this purpose, r . :."':>; The presence of three per cent, metallic oxides in moulding sand impairs its refractory qualities. Still "more undesirable is the presence of Kme, one per cent, of which will make sand undesirable for good castings. Lime present as a carbonate gives off its carbonic acid; gas at the temperature of liquid 1 iron, causing the latter, ; when in contact with the mould,' to form bubbles and air-pass/ages which destroy the smoothness of the surface. If present as caustic, it will vitrify and adhere to the face of the: castings. . . . The best moulding sands are those; that contain the ■■;,largest pro-; portion of silica ; from one to three per cent, magnesia; an entire^ absence of lime with sufficient alumina to render the sand cohesive and, plastic. Sands of the: above description are seldom found in a natural state." ; . I,;';; 1 :' ■ .'';/■ . INFLUENCE OF , THE WIDTH. OF . STREETS ON, '...• PHTHISIS. According to an American contemporary, remarks.' the Lancet, Dr. Anders has been; making certain inquiries in Philadelphia as to the influence of the width of streets on the mortality from phthisis, the wasting away of! bodily tissue, and as the result of; examining into the . localisation of 1590 deaths, he ; has . arrived* at the conclusion; that the number of phthisis deaths. is smaller in proportion to- the population in wide streets ; than; in narrow ones, and that in : narrow streets the mortality is greatest where they ! are long, 'f or where they form ■cul-de.-sac ; in other words, com-! plete movement of air about dwellings is a! point of great importance in connection with the question! of - pulmonary phthisis. It is on this principle that all/ modern bylaws ! as ;to open < space about houses are based, = and it is as important rto v have wide, open spaces behind houses as well as in the streets in ? front, so as to secure a proper through, current of air. There is, as a rule, not* much difficulty in getting a reasonable width of street in the case of newly-laid out/areas for: building, but there is- a ; constant tendency to put an undue ; limit on ! the * needed area ..behind dwelling-houses, although this is a matter of the first importance as regards the promotion of health and the prevention of a certain class of diseases. The observations from Philadelphia deserve the consideration of such sanitary authorities in this country as have hot ,yet acquired proper control over the open spaces to be provided about new domestic buildings. ! ;

/.THE HUMAN ,TOK AND .MOUTH. !; In the anatomical institute at Strasburg, it has been found that • the small i toe of the human nice if) retrograding and losing one of£ts joints, Among 50 small toes dissected, 14 had two joints instead of three; The Springfield Union, under the head of ''Will the ' mouth :ever bite > the ■:. ear says:A Frenchman has discovered that the human mouth is gradually working its way around toward the left ear, and accounts for it by the invariable tendency of men to eat chiefly with the teeth on the left side of the mouth. This wears out the teeth on that side and gives. the jaw a cant toward the left. In the course of a few ages it is believed that the mouth will approach the left ear, and there is some danger, if the process keeps on long enough, that it may get around to thei back of the neck.. • , gold' extraction '.by cyanide. The process of extracting gold from its ores and matrices by the agency of cyanide of potassium. has been put to the test in a. series.of experiments by Mr. Watson, at the instance of the Society of Chemical Industry.! v The : best result obtained ,". by him was 81 par cent, of the actual quantity of gold in the.ore, and 22 per cent, of the silver. y The gold was obtained by .three successive repetitions of tho process, although no doubt more could have been extracted by further repetitions. The process is simple enough, but it is"costly, and the result is obtained with soine difficulty by continued agitation, It is' suitable for realising with low grade ores, but it is not' likely \to become a . good working process unless some cheaper mode of preparing the cyanide is discovered, as well as recovering it from the spent ' materials. ■. The truth seems to be that," although the process is simple, it is troublesome," tedious, and expensive. The actual cosf, is not given, but from , the high price of cyanide it is nob likely to be remunerative.''Something may be {done with it; vbuX it cannot yet be regarded as available ill actual practice.

FIRE-PROOI? SIIUTTJSKS. ■•■'-.'"A. useful invention has been brought to notice—-namely, a device for opening and closing fire-proof shutters from the outside with water pressure from; the hose, and their easyoperation from the ladder, under the management of the fire department. The mechanism, provided for opening and closing the shutters from the inside, without raising the w/.ndows, is a feature of special convenience and protection to theoccupdnts of a building. This device, it is stated, can readily and: inexpensively be applied to the ordinary shutters iii use. . / MISCELLANEOUS. The locomotive engine is said to have a maximum life of ' about 30.' years. The annual/cost of repairs is from 10 to 15 per cent, o'i: its first cost. Mr./ Macleod has procured a patent for a. new mustard pot, which acts like an artist's pain'o tube, ejecting the mustard through a swill nozzle -by ■ compression. By thi3 means the mustard is always in condition. After -much 'study, and many ' experiments, Mr. Alex. P. Wright, of Boston, has produced a flexible glass tube, to serve as a conduit for electric wires, which is said to be perfectly, waterproof, and practically fireproof. The conduit is enclosed in a strong woven jacket, which gives a high tensile strength, and a strong abrasion resistance, and the whole is then soaked in an insulating material. * The system of connections is simple, and ; the cost is quite small. ' '

An alarm for tolling when a ship reaches a certain predetermined depth of water is now being tried on H. M. Rambler in the Red Sea. It consists of a wire sounding apparatus having a sinker which, on coming into contact with the bottom at the depth arranged for, ; relieves the drum on board the ship from strain, and strikes a boll there to raise the alarm. A regular sounding is then taken to verify the alarm of the " sentry," as the new machine, which is the invention of Mr. S. H/ James, C.E., is called.