SCIENCE NOTES.

Otago Witness, Issue 2203, 21 May 1896, Page 48

SCIENCE NOTES.

• . ■It is commonly supposed that the sudden and complete freezing of lakes and watercourses— not an infrequent occurrence in northern regions — must necessarily be fatal to all their inhabitants. Recent experiments by a French scientist, 11. F, Regnard, have proved this to be an error. He cooled the water in an aquarium containing live carp to different degrees below freezing. At 0 deg. 0. the fishes seemed to fall asleep, but were not frozen. A- 3 deg. they were apparently dead, but retained their flexibility. The water being then gradually warmed, they revived, began to swim, and showed no signs of suffering. This would indicate ' that the polar seas, whose temperature never falls below 3 deg. 0., may be a congenial abode for creatnres inured to this degree of cold. • . • Professor Linde is reported to be successful in putting to practical application the researches of Professor Dawar in regard to liquid air, which he proposes to utilise for the. construction of a refrigerating system for in advance for economy and efficiency of anything in existence. ' . ' The early astronomers f oundt hat Venus turned on her axis in 23 or 24 hours, and consequently that her day and night were about the same length as ours. The first to dispute the result was Schiaparelli, the sharp-sighted astronomer of Milan, who discovered the famous " canals " of Mars. Schiaparelli deolared that Venus only turns round her axis in 224 days or thereabouts— ' that is to say, in the time she takes to go round the sun. Her day would therefore be of the same length as her year, or rather her day is practically perpetual, for, as the moon doeß to the earth, she always exposes the same side to tbe sun, and one-hall must be

in perpetual day, while the other is in per- | petnal night. Trouvelot, the well-known French astronomer FJammarion, Leo Brenner, and others have, however, maintained the old figure of 23 or 24 hours to be correct, but Schiaparelli has not lacked adherents; and now M. Perrotin, the director of the Nice Observatory, has succeeded in getting observations which leave no doubt that the periods of rotation and revolution of the planet are equal, and hence that Venus always presents the same face to the sua. * . ■ People seem (said a practical dentist recently) to wonder why it is that dentists use gold for stopping teeth, and are inclined to belitva that it is because they wish to run up the bills. As is well known, silver would resist the acids found in the mouth almost as well, and I have been asked at least twenty times why I did not use silver. If those wbo are so anxious to oast aspersions on the dentists would only study metallurgy, they would find that the reason that we employ only gold is that it is the only metal that will weld whilo cold. Silver will not do so, nor will anything else. The cohesive properties of perfectly smooth and clear gold are astonishing. If you take a sheet of gold foil and let it fall upon another, both will be so firmly joined that it will be impossible to separate them. It is this property that makes gold valuable to dentists, and not the desire to increase bills. • . • The latest development in photography appears likely to effect a revolution in "the art, since by its agency it is claimed that 1,000,000 portraits can be produced ready packed in 10 days if necessary— a number almost impossible to be prepared in the ordinary way. From 60,000 to 70,000 photographs a day are said to be the normal outturn of the new invention, which, as will be seen from the subjoined description, is not very unlike a modern newspaper printing press in its method of working. Six or seven ordinary negatives are put in a frame, side by aide, the string of them thus formed being placed in the printing machine. A roll of prepared bromide paper is suspended or pivoted at one end of the machine, and the end of- the paper is started through. In the half- cylindrical exposure box containing the negatives an intense light is then produced by means of eight incandescent electric lamps. When all is in readiness a platen bslow presses the paper up against the negatives, the light is turned on, and an exposure of one or two seoonds is made. Instantly the lamps go out, tbe paper is pulled along by a winding-up device, and the operation is repeated. When one or more of the negatives are lens intense than their fellows, and the ordinary exposure is found to be too long, thin sheets of waxed or tissue paper are pasted over, in order to filter the light rays and render them less active. The remaining processes of developing, fixing, washing, &c, are gone through in a similar manner, until the roll of photographs is ready to be cut up and mounted in the usual way. • . • Much of the rich sculpturing in the U.S. new congressional library building is being done by the use of anew invention in the shape of an air chisel. By the use of this marvellous little machine the modern statue is carved quickly and with a precision almost equal to the old masters. Of course a model in plaster is necessary, the compressed air chisel being used simply for reproduction. The tool is not unlike the dentist's drill. It runs under about 301b pressure and strikes .a blow between 1200 and 1500 times a minute. An expert does excellent work with this machine, which cuts marble as easily as the carving of steamed wood. * . * The following are substantially the conclusions reached by Drs J. S. Billings, S. Weir Mitchell, and D. H. Bergey regarding the composition of expired air and its effects upon animal life. There is no peculiar organic matter which is poisonous to animals (excluding man) in the air expired by healthy mice, sparrows, rabbits, guinsa pigs, or men. The injurious effects of such air appeared to be due entirely to the diminution of oxygen or the increase of carbonio acid, or to a combination of these two factors.' In ordinary quiet respiration no baoteria are contained in the expired air. In the act of coughing or sneezing such organisms may be thrown oat. The minute quantity of ammonia, or of combined nitrogen,, or other osidisable matters found in the condensed moisture of human breath, appears to be largely 13 ue to products of the decomposition of organic matter which is constantly going on in the mouth and pharynx. The air in an inhabited room, such as a hospital ward, in which experiments were made, is contaminated from many sources besides the expired air tf ooonpauti, and the

most important of these contaminations atf£ in the form of minute particles or dusts. The experiments on tbe air of the hospital ward showed that in this dust there were mioro* organism?, including some of the bacteria which produce inflammation and suppura^ tion, and it is probable that these were tha only really dangerons elements in this air.— Appleton's Popular Science Monthly (New York). • . • On a fine day clouds are often four or five miles above our head?, bat their average is only from one and a-balf to two miles'/ Clouds in thunderstorms, or giving oat eled* trioal discharges, are eometimea at the great altitude of four or five miles. At other times they nearly or quite touch tbe earttf, but they are seldom discharged in a thunderstorm when they are more than about 700y<3« above the earth's snrface, or about half & mile. | *.'A complete and immediate revolution of transportation methods, involving a reduction of freight charges on grain from the West to New York of from 50 to 60 per cent., is now predicted. The plan proposes using light and inexpensive oorrugated iron oylinders, hung on a slight rail supported on poles from a cross-arm, the whole system involving an expense of not more than 1500dol a mile for construction. Tbe rolling stock is equally simple and comparatively inexpensive. Continuous lines of cylinders, moving with no interval to speak of, would carry more grain in a day than a quadrupletrack railway. This would constitute a sort of grain pipe line. • . • There are several large lumber mills in Deseronto, Canada, and the town is partially lighted t>y gas obtained from sawdust from them. The sawdust is charged in retorts which are heated by a wood fire. The gas from these retorts passes into a series of coils, and thence into the purifiers, which are similar to those ueed for coal gas. Lime is used as a purifying agent. The plant is not a very large one, and it only turns onfc 510 cubic metreß of gas per day, for whioh about two tons of sawdust are required. A man and a boy furnish all the labour needed at the works. The best quality of gas comes from resinous woods. One hundred kilogrammes of sawdust leave a residue of 20 kilogram meß of charcoal, and the gas in an ordinary burner (says the Engineering and Mining Journal) gives an illumination of about 18-candle power. [ • . ■It would not be a wild prediction to say that persons now living may read of a vessel leaving Liverpool, passing through New York harbour, up the Hqdgon River, through a caual to Lake Erie, thence by Lake Michigan to Chics go, down tbe Chicago canal into ihe Mississippi, thence up the Mississippi into the Missouri, up that and thence by canal to the Columbia River,* and down that into the Pacific Ocean, and thence back by way of the Suez Caual, thus circumnavigating the globe and crossing the North American Continent.