Scientific and Useful

Bruce Herald, Volume XXI, Issue 2178, 27 June 1890, Page 6

Scientific and Useful

RIVER FORCE.

According to a Baltimore paper, it iB proposed to uae tho great fulls of the Potomac River, 16 miles above the city, to force compressed air to the city to operate electric-light plants by pneumatic power. AOB OF BRONZE IN EGYPT. M. Montelius, in opposition to tbe opinions of Lepsius and Maspero, belie res that the use of iron was not known in the valley of the Nile as early as bronze, which was probably fabricated in;6oooß'.c, and thatthe use of lhe former metal wns not sufficiently common to justify ns in speaking of it Iron Age in Egypt before 2000 B.C. He, moreover, believes that we must consider tho era of Egyptian civilisation as belonging mainly to the Bronze Age. AUTOMATIC SAVINGS BANK. The apparatus delivers a perforated cheok to each person depositing one penny. This must be torn in two, the name and address of the depoeitor written on one half, aDd dropped into the nick again, the other half being retained for withdrawal from the central office. Fraud by the insertion of card or metal discs is detected by the half check being stacked next to the depositor's coin. The boxeß are periodically cleared, and depositors credited with amounts corresponding with the checks. This maohine might be advantageously used in connection with schools. WEIGHT OP EARTH MATERIAL. The solid crust of the earth on which the water-envelope rests is tne cooled-down portion, which projects here and there above the water to form the "dry land." Geologists tell us tbat a fair estimate is to assume tbat the rocks whereof the globe's crust is composed show a weight which may be taken to be twice or thrice the weight of water. This statement however, requires modification. For when we measure the earth's attraction we find that the density of its materials rises to an amount equal to five times that of water, or even a little more. This seems to imply that the inner part or core of our world consists of very heavy matter ; some authorities agree in regarding the centre as being of metallic nature, and that the substance of our planet may really be pictured as being dispoeed in layers, whereof the innermost are the heaviest of all. SEABCH-LIG-HT EXPERIMENTS. At San Francisco harbour experiments bave been made with the Huttington electric search-light. The search-light hitherto used on American warships is usually a very heavy apparatus, and made in France, weighing about 10001 b., and cost about .£2OOO. Tho new search-light weighs only about 1301 b., is of 4000 c.p., and coat £72. One man can easily handle it, and the light is concentrated in parallel rays, instead of being diffused over a wide area, as in those previously used. At the distance of half a mile on a dark clear night buoys could be plainly seen, and every rope in the rigging of a ship. It is claimed that the light will penetrate the thickest fog sufficiently to prevent collisions. An interesting experiment was made by turning the beam vertically, when a column of light threequarters of a mile high is produced, visible on dark, clear nights many miles away, and visible in the thickest fog at one-eighth of a mile distant. THE COLOURS OP A SUNBEAM. We speak of the sun's lighf us colourless, just us we speak of water as tasteless, but both of these expressions relate rather to our own feelings than to anything really characteristic of water or of sunshine. We regard tbe sunlight as colourless because it forms, as it were, the background on which all colours are depicted. The fact is that white is so far from being colourless that it contains every hue known to us blended together in certain proportions. The sun's light is really extremely composite. Nature herself tells us this if we will but give her the slightest attention. Whence come tbe beautiful hues with wbich we are all familiar? Look at the lovely tints of a garden ; the red of fche rose is not in the rose itself. All the rose does is to grasp the sunbeams which fall upon it, extract from these beams the red which is in them, and radiate that red light to your eyes. Were there not red rays commingled with the other rays in the sunbeam, there could be no red rose to be seen by sunlight. — From " The Story of the Heavens."

WIND MEASTTBEMENTS OW THE EIFFEL TOWER.

Although the scientific uses of the Eiffel Tower have been very limited, some noteworthy results have been obtained from fche measurements of the speed of wind made on it. The indications were taken simultaneously by two Richards anemometers at the top of the tower, at a height of 305 metres, and on fche observatory station of the Meteorological Central Office, at a height of 21 metres, and extended over 101 days from June fco Ootober last. Tbe mean velocities obtained from them show that fche speed at the top of the tower varied from 848 metres per second at midnight, to 504 shortly before noon, increasing again to the former during the afternjon ; while at 21 metres the speeds range from I*Bs metres at midnight to 3*19 shortly afternoon, decreasing again to the former. The variations are tolerably regular, but follow opposite laws ; while in the neighbourhood of tho soil the highest speed occurs about noon.it is at a height of 300 metres lowest at this time. The mean velocities for fche entire day are 7*05 metres for tbe higher, and 2-24 metres for the bwer level, or three times as much at the top of the tower, a considerably larger variation than was expected. — Mechanical World. WBATHBB FORECABTS. We have received, says Nature, from Mr D. Dewar his " Weather and Tidal Forecasts for 1890." The author has previously published similar forecasts for paßfc years, and fchey are said to be mainly based upon the simple idea thatthe prevailing westerly movement of the air in the two great belts in the north and sooth temperate zones is due to the continued westerly (west to east) movement of the sun and tho moon, and it iB claimed that the probable weather, while referring generally to the northern hemisphere, is chiefly applicable to the British Isleo and neighbourhood. We have made a rough comparison of the forecasts with the actual weather experienced in the British Iblos during the first three months of this yoar. The weather predicted by Mr Dewar for January largely consists of cold and anticyclones, whilst the actual weather experienced was conspicuous for the absence of cold, with the exception ofthe fiist two or three dayp, and its mildness probably exceeded that of any January during the last half century. At Greenwich the thermometer did not onre fall below the freezing-point after the 3rd. Considering February, as a whole, the foreoasts were rather more successful. In March the early part of the month waß to have been mild, except in the north. The first few days were colder than in any March during the last half century, except in the north, where milder weather waa experienced. The weather predicted for the remainder of the month consists almost wholly of cold and snow, whereas tbe weather was exceptionally mild, and the Greenwich temperature on the 28th has only twice been exceeded in March during tbo Ust fifty years.