SCIENCE & INVENTIONS.

Nelson Evening Mail, Volume XLVII, Issue XLVII, 7 March 1912, Page 2

SCIENCE & INVENTIONS.

ABSORBING FLOODSAbsorbing fiood water by storage wells is a plan French engineers are considering. Much damage was formerly done by inundations oil the estates of the Count of Beauchamp, between Portiers and Avalon, but this has been remedied by. digging wells 50ft to 60ft deep, and leading to*!their vicinity by ditches. Percolartcm of the water through a porous layer frees the water from mud that otherwise would soon fill til' th« Wolls.

NATURE'S PARACHUTE. Careful examination has been made of the heads of Canada thistle-downs, in. order to determine their effectiveness as parachutes, carrying the seeds of the plant to great distances through the air. The results of this examination are quite remarkable. Calculation shows that a thistle-down starting from an elevation of 20ft, in still ai'r, wfUild require twothirds of a minute to reach the ground. With a wind blowing 20 miles an hour it would be carried, on an average, about a fifth of a mile. The total surface exposed to the air in an average thistle-down is, on account of the great number of hairlets, a little more than one-third of a square foot. Another wellknown and very beautiful example of Nature's parachutes is furnished by the light silken threads with the? aid of which the liltle gossamer spicier makes long aerial voyages. NEW WAY OF STUDYING MARS.

Photographing through coloured screens is the newest method of studying Mars that has been undertaken by Tik-. hoff at the Pulkova Observatory. Four different screens were iVsed —transmitting respectively red; red and orange, orange and yellow, and green—and in the iSO-inch equatorial telescope they produced good photographs of very small size. The red add gi'eell filters have strikingly different results. On the plates that were exposed under the red, the continents are much brighter than the south polar cap, while the seas are ; very dark, and the canals are the best seen; an'ij, the pictures that were taken under the green show the south polar cap as the brightest object, and the seas are greyish. A study of the polar ,_ip has made it appear greenish instead of : white. The interesting conclusion has been reached that at the time the photographs were made the cap was ice ii> stead of snow, and this view has been; confirmed by experiments on the absorption spectrum of ice and in photographing sand, snow, and ice. THUNDER. it has usually been thought that the' noise of thunder is caused by the closing up of the vaccum treated by the passage, ot tiie lightning, the air rushing in from all sides with a slap; but the intensity of the noise is rather disproportionate, and it is now supposed that thunder is due to the intense heating of gases, cs- : pecially the gas of water vapour along the line oft electric discharge, and the consequent conversion of suspended moisture into steam at enormous pressure. In this way- the crackle with which a peal of thunder; sometimes begins might be regarded as the sound of steam explosion on a small scale, caused by discharges before the main flash. The rumble would Bp the overlapping steam explosions,, and the final clap, which soimds loudest, would be the stearii ex plosion, nearest to the auditor. In the 'Cftse of rumbling thunder the lightning is passing from cloud to cloud. .When the flash passes from.the earth to the clouds the clap is loudest at th'e":.bcgnining. . Trowbridge gave substance to these suppositions " by causing electric flashes to. pass, from point to > point through terminals clothed in soaked cotton wool, and he succeeded in magnify ing the crack of the electric st>ark to a terrifying extent. ICEBERGS.

• Among the perils .arid '-wonders of the ocean there are few more interesting things than icebergs, interesting rfot only by reason of their gigantic size, their fantastic shapes, their exceeding beauty, but -also for the manner in which they array themselves. Icebergs exhibit a tendency to. form both clusters and long lines, and these groupings may aiise from effects both of ocean currents and of storms. Some very singular lines of bergs, extending for many hundreds of miles east of Newfoundland have-been shown on official,charts issued by the Government. "Two of these cross each other, each keeping on its independent course after crossing. . In several instances parallel lines of bergs leave long spaces of clean water between them. Curiously enough, while enormous fields of ice invade the socalled "steamer lanes" of the Atlantic at the opening of spring during certain years, in other years at that season there is comparatively little ice to be seen. The ice comes, of course, from the edges of the' Arctic regions, from the ice-bound coasts . of Greenland and Labrador, where. huge bergs broken from the'front'of the glaciers at the point where they reach the sea, start on their long journey toward the south, driven by the great current that flows from Baffin's Bay into the northern Atlantic Ocean. . THE PHASES OF PLANETS. "We are likely to regard the moon as the only thing in the heavens that exhibits phases such as the quarter, the half, arid the frill. As a matter of fact., all planets and their satellites exhibit separately such ' phases, and most of them can be easily seen ' with a smallpower telescope (says an exchange). Thus, Mars and Venus, which are comparatively close to the earth, show through the telescope at times a beautiful crescent, at others a half planet fully as brilliant, considering the distance, as does our satellite. At times also the planets suffer eclipse, just.as the earth the moon, and tiie'sun, and these eclipses are foretold with, as great accuracy. As to just what causes the phases, say, of tile moon, is easy to comprehend by a homely analogy. If one stands in a. corner of a room, places a globe of some description in the next corner, and a light in the third corner, the phenome- I non of the half-moon is seen. The light representing the sun shines, of course, on half the globe representing the moon ; but the observer in the corner sees only j half of the surface toward him illuminated. If now the light be placed behind the observer, and a little above his head, a full moon will be seen ; the "sun," however, shining on the same area of surface as. before, merely allowing this time a view from the . "earth" of the whole amount of illumination. All the phases can be demonstrated in this manner, by moving the "moon" directly outward from its corner.^ PIGMENTS FROM ODD SOURCES. The ingenuity of the manufacturers of pigments for the use of artists has been so severely taxed within recent years that they have been obliged to employ for the purpose rtll manner of animal, vegetable, and even mineral substances. Even Egyptian mummies have been utilised in this way by the manufacturers. It appears that the corpse of the old Egyptian was preserved in uie

finest bitumen, and that the/remains thus treated, in the centuries gpne; present, on being unwrapped to-day,' an appearance quite like that of lightcoloured leather. Now it has been discovered that, when the bitumen and the leather-like- remains are ground down by machinery, there is obtained therbfrom a beautiful brown pigment, especially prized "by painters of portraits, who claim that this pigment is particullarly effective in depicting certain shades of brown hair. Among the other colours obLained from strange sources may bo mentioned Prussian blue. This is made by fusing the hoofs of horses with impure potassium carbonate. Sepia is the 'dark fluid discharged by the cuttlefish to' render the water opaque for its own concealment when attacked by its enemies. The cochineal insect furnishes crimson and purple lake and .carmine ; while ultra-marine is procured from the mineral known as lapis lazuli. Ritiv sienna'is natural earth from Sienna, and, when burnt, becomes burnt sienna. Gamboge is- the yellow sap of a .tree that grows in Siam.