The Birmingham age-herald., 1911-12-10
WHERE IS WORLD ID GET FOOD SUPPLY? Some Interesting Figures
 From London NOTES OF SCIENCE Analysis of Effects of Darkness of Deep Sea-When Ears Fail to
 Distinguish the Various
 Sounds
NOTES OF SCIENCE
From the London Morning Post.

From the London Morning Post.
 Tn the attempts to forecast the future populations of countries and continents the statistican has sometimes set against calculations based on the normal or differ ential rates of increase the check afford ed by the supply of food. Populations can not increase beyond the point at which there is enough to feed them; and unless man possesses enough adaptability to eat the synthetic proteids which science may succeed in making for him, we should be inclined to say that his numbers must be limited by the amount of ground that can be brought under cultivation, and the amount of sea on which his fisheries can levy a contribution. But the calculations of the periods at which wheat GOT coaD, or any other of mans necessities will fail have hitherto proves rather unsatisfac- tory, and have been continually subject to revision as new sources of supply have been discovered. If that were not so the world, according to very care full estimate made in 1898, would begin to starve in 1881. Is there any basis for computing the limits of productiveness?
 Dr. ". J. McGee in examining the wide- ly differing estimates of the ultimate pop ulation of the United States, which the latest computer, Henry Gannett, puts at 250, ,000, 600 go years hence-points out that a practical limit to the productivity and habituality of country is fixed by limit alton in it's water supply. Tn arid lands like Egypt careful calculations have been made of the amount of water necessary to
 
 many inches of water year, let us say 30. before it will raise enough vegetable food to keep one person. Thirty inches is under the mark, because man does not live by bread alone, but on meat, and the animals which give him that have also to be sustained by vegetable food The man who eats POO pounds of bread and 200 pounds of beef year drinks in the same time a ton of water, and the equivalent of 400 tons of water which have gone to make the bread. and 4OOO tons of water which have gone to rear the beef-4i00 tons of water in all Consequently the water supply of a country in which man is to | live must be always equal to something | over 40o0 tons per individual. The an- | nual rainfall of the countries of the | northern hemisphere is about 30 inches, | only half enough to fertilize one acre to a sufficient extent to keep a man. | Roundly speaking, perhaps one might say | that the worlds supply is sufficient to l keep a population of one man to every l two acres.
 Darkness of Deep Sea
 A mile below the surface of the sea no light penetrates; the darkness is more in- tense than that of the darkest night; at 100 metres the ultraviolet rays, which the eye does not perceive, would be per ceptible to a photographic plate; at half iGf the blue and violet still penetrate. In the investigations which Dr. Hjart has made in the North Atlantic he has found that below this 800 metre level the fishes taken are black and the prawns are red. Nearer the surface the fishes begin to have larger eyes and silvery sides. The inference is that the region which are red rays of sunlight pene- trate, and the darker region to which they cannot reach. are characterized by difrer- ently colored kinds of fishes, and that the difference of color arises possibly from the amount of light they receive, possibly as the result of an attempt at protective coloration. Some interesting observations on the theory have been fur nished by Dr. C. V. Burke, who has been doing similar work in the Pacific, though confinng his attention to one species of marine life. In a region of total dark ness, he points out, the color of an anil nal could not be an aid to concealment It might just as well be brilliantly co., ored as transparent or black. But there is no denying that the coloration appears to depend on the amount of sunlight to which the species are subjected. There are two possible sources of light in the oceanic depths below the penetration of sunlight. Certain animals of this region have light producing organs; and decom- posing animal matter also may give forth a phosphorescent glow. And, as if for the purpose of sight in dim light, the eyes of the fishes have become greatly en- larged. Contract now the effects Of dark ness in cave fishes. These do not need protective color, for there are no enemies to be protected from. They lose their pigment, become paley white and their eyes become atrophied. The ocean fishes, surrounded by other fishes with large eyes and hostile teeth, acquire pigment and become wholly black. Possibly the eff feet of the rays of light Is the warp and the struggle for life the wool of the coloration of fishes.
 Ears Acute to Sound
 Those of US who have reached what novelist lately called the prime of early middle age may have remarked during, our holidays a noticeable quietude in the bats that wheel overhead at sundown. Closer observation may have disclosed the fact that while the rustic of their leathery wings could be detected as they flew by, yet the shrili squeak so char acteristic of the bat was absent. The req son was to be sought in our own ears. The hearing of many persons, while remaining apparently as capable as ever of noting light sounds, becomes after 40 or even earlier unable to detect very high pitched sounds, that is to say, sounds which are produced by very rapid Vibrations. The human ear, at it's best, can hear sounds which range from 30 to 40 vibrations a second Che lowest musical note) to 3s,0o0 vibrations a second. But many persons with average powers of hearing are deaf to vibrations of 13,OCO a second. Old peo- ple often lack the ability to distinguish the letter "s' distinctly. The reason is that the hissing sound when analysed into a