Scientific Notes.

Otago Witness, Issue 1586, 15 April 1882, Page 29

Scientific Notes.

How Mist is Produced.

It is quite easy to understand, under the suggestion of the direct observations by Sir Humphry Davy, why it is that night mists so commonly hang over the surface of large rivers until they are dispersed by the beams of the risr ing sun. The cooling of a considerable body of water necessarily takes a longer time than the cooling of a corresponding area of solid ground. The cooling of the ground is restricted to a very moderate depth, because the heat from below does not travel up to the actual surfaoe as readily as it radiated off from that surfaoe into the air. But whenever the immediate surface of any considerable collection of water has been reduced to a, temperature of about 45 deg., that portion of the liquid grows heavy and sinks, .and warmer water from below rises up to take its place. On this account the surface of water cannot become the coolest part of the mass until the whole has been chilled to something like 40 deg. Water, therefore, which has acquired about the same temperature as the neighbouring land by day generally remains warmer after sunset and through the night. Its comparatively high temperature is sustained.

by the store of heat which is being continually brought up towards the surface fromthegreater depths. The air above the land thus habitually becomes cooler at night than that above the water. The air is kept warm by the water and cooled by the land. If, therefore, in both situations it contains the same' inherent amount of aqueous vapour, some portion of this is precipitated as mist whenever the cold air of the land is mixed with the warm air of the water, and the precipitation is the more abundant in proportion as the surrounding land is higher, the water deeper, and its temperature greater. Mist occasionally forms over grass when adjoining bare ground is clear, simply because the rapid radiation of heat from the grass more speedily brings the superjacent air to a temperature low enough to produce the condensation of its vapour. When newly-ploughed ground becomes covered with mißt -whilst the neighbouring pastures' remain clear, that is due to the circumstance that the freshly turned up soil is warmer than the grass, and in a state more favourable to the copious emission of its moisture as vapour. ' The effective cause of the production of mist is the sudden chilling of warm moist air. But it is quite immaterial now this is brought about ; it is of no consequence whether the chill is applied from above or from below. In the case of a broad and gently flowing river, such as the Thames, the chilling influence most commonly' acts from above ; but it is quite possible, even with a running stream, that matters may be reversed. Sir John Herschel has drawn attention to the circumstance that cold mountain streams, cover themselves with mist as soon as they reach low and comparatively warm levels of the atmosphere. In such instances they carry in themselyes the cold which is essential for the condensation of the vapour, andthe mist appears because the air is warmer than the water.— Science for All.

The Electric Candle In Vacuum.

Sir Humphry Davy was the first to note that the Voltaic arc became longer when confined in vacuum, and that the carbons were not consumed. In Jamin's experiments with the electric candle in vacuum, it has been found that when thus confined, or when hermetically sealed in vessels containing inert gases,the carbons are not acted upon. Such a gas is nitrogen, acetylene, carbonic acid and marsh gas. Most other gases are decomposed by the arc ; for example, steam gives carbonic oxide and acetylene, carbonic acid doubles its volume, and changes into carbonic oxide, and the hydro-carbons, especially vapour of petroleum, is decarbonised, and produces filaments of coke connecting the carbon points. This action is employed to good purpose in fabricating the carbon loops for the Maxim incandescent light. Air in the sealed vessel offers a peculiar interest. First there are seen vapours produced by the combination of oxygen and nitrogen ; but this combination is soon destroyed, and the gas appears colourless again, because of the oxygen combining with the carbon, Nitrogen and carbonic oxide then remain in the vessel. While the hyponitric acid vapours are in the vessel the arc changes in tint and elongates ; but at last, when the chemical transformations are complete, the arc is good and of a greenish blue. The important point, however, it is stated, in a practical sense, is that it becomes quite fixed, and varies neither in colour, position, or intensity, as all naked arcs, however, well regulated, still do. The spectrum is that of carbon raised to incandescence without burning, a spectrum such as has been observed in the tail of the recent comet by M. Thollon. On the other hand, the spectrum of a naked arc glowing in the air is complicated by that of burning carbon. In an inert gas, therefore, the arc is a purely electric phenomenon, and it can be directed by electro-magnetic action. The ordinary arc, again, is composed of this electric incandescent current, and the flame due to the burning parbons and their irregular waste. The cessation of burning also stops the waste of carbons. When the Jamm candle burns in the open air it is consumed at the rate of 16 millimeters • per hour; when closed in a sealed vessel this consumption is reduced to 0.2 millimeters per hour. Each candle lasts 160 hours, or 16 times longer than when burned free, and each lamp 800 hours, or 80 nights of 10 hours each. Not only the fixity of the arc, but its durability, is thus very much increased.— lron Age.

Halos and Rainbows of the Moon.

Complete circles of ,faintly coloured light are sometimes formed round the moon on nights when the sky is thinly veiled with haze. The iridescent rings in such circumstances are familiarly spoken of as lunar glories or halos. In its most characteristic and complete state the circle has a diameter of 45deg. of the celestial sphere— that is, it is. a ring-shaped band of light concentric with the moon's face and just 45 times that luminary's own breadth away from it. The colour is generally very subdued, but it is occasionally so well pronounced as to render the halo liabl& to be mistaken by unpracticed observers for a lunar rainbow. The distinction is, nevertheless, absolute and clear. The halo encircles the moon, and therefore appears on the same side of the sky, whereas the rainbow of neoessity presents itself on the side of the sky which is opposite to the moon. The observer stands with his faoe to the moon whilst looking at a halo, but mast have his back to the moon while he is contemplating a rainbow. Circles of a similar character are occasionally formed round the sun, and they are not as easily observed on account of the overwhelming glare of the solar light. Whenever the colour is well developed it is found that there ia a red tint at that edge of the luminous band which is nearest to the moon, or sun, and a blue one at the opposite margin. The halo thus produced round the moon or sun is due to the influence of minute prism-shaped crystals of ice, floating in g^reat abundance in the higher regions of the air.— Science for All,

Odds and Endn.

The attempt hos been made, by means of the photophone, to make audible sounds produced in the sun.

■ Professor Schlager, of Vienna, is responsible for the statement that blue light h&s a quieting and soothing influence on the % insane,. The smoke-abatement exhibition is aajd to have shown that " it is easy $0, raise any quantity of steam without showing smoke at the chimney." The Paris Electrical Exhibition was set on fire five times by eleq.trao lights—a significant indication of the need ot speoial precautions in introducing these lights. Celluloid is now being used in the manufacture of artificial eyes. The material is lighter than glass, and its non-friable quality renders it far more trustworthy in emergencies. A new hydraulic ship has been tried in Germany, and succeeded in making nine knots an hour. She is driven by forcing water out of tubes with narrow outlets plaoed in the stern.

One of the latest theories advanced is that apples are more nutritious than potatoes, and in Cornwall, England, workmen say they can work better on the fruit than on the vegetable. Professor Huxley says that those , who have taken an active part in science should be killed at 60, as not being flexible enough

to yield to the advance of new ideas. He is himself nearly 57. , , The use of steel for marine boilers and other work of the same nature has been a good deal criticised of late. It is objected that steel is easily; made brittle, and is not a trustworthy substitute for iron. If the English language were divided into 100 parts, 60 would bo Saxon, 30 would be Latin, including, of course, the Latin that haß come to us through the French, and five parts would be Greek. The movement of railway-trains by electrical means seems likely to be a matter of some practical importance. A successful attempt has been made in Italy, The trains are said to cost less and make less noise than those moved by steam. A calculation of the height of the atmosphere has been made by Herr Ritter, in which its caloric state is used for this purpose. His result agrees well with that by Schiaparelli from the observation of falling stars— viz., about 200 miles.

J. Gillingham claims to have discovered that, with a proper instrument, sounds can be conveyed to the mind through any set of nerves in the body, and also that the vibrations of light, by the aid of electricity, may be made to convey the sense of sight in a similar way through the nerves.

E. M. Boynton, whom the New York Sun describes as a Brooklyn inventor, and who hails from Massachusetts, has patented what he terms a bicycle railroad, by which he expects to revolutionise the present system of railroads, and to enable people to travel at the rate of 150 miles an hour.

The Clarks of pambridgeport, Mass., are making a refracting telescope, larger than any now in the world, for the Russian Government. It will have a clear aperture of 30 inches. The same firm are making the telescope for the Lick Observatory, which will have an aperture of 36 inches. J. H. A. Macdonald, the late Solicitorgeneral for Scotland, has constructed an "electric holophote course indicator," which he has lately been exhibiting in Edinburgh. An electric light with a reflector is placed in a prominent position on the deck of the vessel, , and is controlled by the movement of the helm. The direction of the powerful^ beam of light indicates the course of the ship, and at the same time shows whether or not the sea is clear over a large area. An exhibition was made at the Paris Exhibition by John Mackenzie of an improvement in telegraphy, which promises to become of much importance. By this device it is claimed that any number from 1 to 999 can be auto-; matically signalled on one wire by a single, movement of the transmitter, so that on opening the box at the receiving station the number wul be found correctly recorded. It may not be generally known, says London Truth, that a man wearing dark clothes is more liable to infection from contagious disease than he who wears light-coloured garments, because particles which emanate from deceased or decaying bodies are much more rapidly absorbed by dark than by light fabrics. This is easy of proof. Expose a light and dark coat to the fumes of tobacco for five minutes, and it will be found that the dark one smells stronger than the other of tobacco smoke.

In 40 Government schools in Saxony, observations have lately been made as to the temperature, carbonic acid, and moisture of the air with different kinds of heating— hot water, air, and stove. It proved that air heating gives' the best results, the least variation of temperature, much the least proportion of carbonic acid, as measured in the middle of the room, at the height of a table, and the smallest variation of the moisture. The ventilation in both the other systems was unsatisfactory.

For more than a year and a half my face was covered with pimples and blotches. Four bottles of Bristol's Sarsapakil&a, and three.of Puts, have entirely cured me.— David Barr, Sandhurst, Viotoiia.— f Advt.]

Murray and Lanman'b Florida Watbrls prepared exclusively of the vary finest and pureit floral ingredients, all of which are ■elected in the best markets, and we are safe in saying; that It is impossible to produce a fragrant water of a better quality.— [Advt.l

Burnett's Aqua db Florimk&, an exquisite perfume for the handkerchief luting and fragrant.— f A»VT.] The superiority of Burnktt's Flavouring Extracts cODßists la their perfect purity and great strength. They are warranted free from the poisonous oils and acids which enter into the composition of many of the factitious fruit flavours now in the market. —[Advt.l

Burnett's Essbnob of Jamaica Ginger, a house* hold remedy for colic, cholera morbus, colds, chilli, and diarrhroa, —arming and stimulating the whole system. Bates, Sise, and Co., agents.— [Advt.]

Thames street Industries, by Percy Russell. This Illustrated Pamphlet on Perfumery, &c, published at (3d, may be had gratis from any chemist in the world, or John Gosnelii and Co , London.— [Advt.]

Smaiili capitalists wishing; to,establi«h a business should see If there is an opening lor a Mineral ,Wator' Manufactory in their district. All Information and' recipes for the purpose of making lemonade, sodawater, &c, is given— previous knowledge Is not, necessary. The demand for these drinks it so much on the lnoreaie, in all parts of the world, that the outhy for the maohinery in all cases leads to a profitable and safe business. Catalogue forwarded free, or can be had at the office of this paper on payment of la.— Barnbtt and Foster, engineers, 280-Forston street. London. N.— [Advt.

Abtiob to Mothbrs I— Are you broken in your rest by a lick child suffering with the pain of cutting teeth! Go at once to a chemist and Ret a bottle of Mrs Wwslow's Soothing Syrup It will relieve the poor sufferer Immediately. It ia perfectly harmless and pleasant to taste, it produces natural, quiet (leap^ by relieving the child from pain, and the little cherub awakes "ai bright as a button." It soothes the child, it softens the gumi, allay* all pain, relieves wind, regulates the bowels, and is the best known remedy or dysentery and diarrhoea, whether arising from tsethicg or other oauies. Mrs Window's Soothing Syrup is sold by medicine dealeu everywhere at Is lid per bottle.— (A.nvi.l i

Manufacturers and others desiring representation throughout the Province ot Auckland should 'communlcate with the undersigned, who his exceptionally advantageous facilities for introducing "novolties" and "specialties" of every description, and is thoroughly acquainted with the trade of the district and its standing. W* businesi premises are simply the most central in Auckland, and his representatives travel the country. Highest reforenoeal W. Bartimw) LangbWW. Manufacturers' Agent and General Importer, " The Bureau." Auckland — f Advt.}

FfcORUiINH !— FO* TOT TISTH AND BKKATH.— A. tow drops of the liquid " Jlorlline" sprinkled on a wet tooth-brush pvoduoei ft plesuant lather, which thoroughly oleansei the teeth from all parasites or impnritloH, hardens the gums, prevents tartar, «top» decay, gives to the tooth a peculiar pearly-whiteness, and a delightful frayronae to the breath. It removes all unpleasant odonr arlilng from decayed teeth or tobacco smoke. "The Fragrant FlovUiae," being composed in part of honey and sweet herbs, U deli oiousto thotaate, and the steateai toilet discovery of tho age. Price 2s 6d, of all Ohomist.ii and Perfumers. Wholesale depot removed to 83 Farringdon, road. London.-fADVr.]

Ekjoy LiffH,— What a truly beautiful world wa live in ! Natura gives us grandeur of mountains, glens, and oceans, and thousands of means for enjoyment. We can Ueßiro no better when in perfect, health ; but how oiteu do the majority ot people foal like giving It up disheartened, dlbcourageti, and wornail out with disease when there is no cccasion for this feeling, as every Bufferor can easily obtain autUfactory proof that Ghkbn's ArouaT Fuowkb. will make thorn as free from (liaise a» when born. Dyspojwlft and Liver complaiut is the direct, cause of 75 per cent, ot such maladies an Bilioußncßß, IndiKe&tion, Bick Headache, Oostlvenesa Nervous Prostration, Dizziness of the Head, Palpita tlon of the Heart, and other distressing symptoms" Three doses of August Fu>wk& will prove It* wonder, ful effect. Sample bottle, 9d. Try it — Sole wholeial■gratis KiMmroaws, Paoawa, and Co.--lAml

V-iIiTJABLB PISOOVXKT 70S IHB H—K.— lf yOUT h»ix 1b tnrntof? grey or white, or falling oil, we " The Mexican Hair Renowar. ' for it will positively restore In entry cau Grey or finite Hair to its original colour, without leaving the disagreeable small of inovt " Beatorers." It makes the hair charmingly beautiful, as wall R9 promoting the growth 0! tho hair on bald •pots, whore the glands are not decayed. Ask yotur Chemista- for "Tub Hhucan Hint Rbnhwbr." Sold by Ohemteta and Perfumem everywhere at 8s 6d per bottle. Wholesale dopot removed to 88 Farringdon road, London [Asyt.]

>»