Page:Popular Science Monthly Volume 2.djvu/660

640 on the subject of malaria, Dr. Rey urges upon the inhabitants of malarious districts the adoption of every safeguard against becoming chilled. He considers the chill, often felt in warm climates at sunset, as very pernicious, and agrees with all authorities in pronouncing cold, with damp, to be exceedingly dangerous. Residents in lowland or damp situations should, therefore, take special precautions to keep the circulation in such a condition that the extremities are not cold, and the surface generally is comfortably warm. By maintaining this condition of body, other diseases besides the so-called malarial would also be warded off.

American Journal of Science and Art has a letter from a correspondent in Mississippi who states that beavers are on the increase in that State, as also in Alabama. When the writer first settled in Hinds County, Mississippi, thirty-five years ago, he could scarce find one beaver-dam in the vicinity of his residence; but, in 1850, every considerable stream in the county had its dams, which caused serious injury to the low lands. A few years ago a trapper caught over seventy beavers in less than one month's time within the limits of the county. The animals are still multiplying, and the writer has no doubt that this is true, not alone of his particular locality, but of all Central Mississippi and Alabama.

of the London Times, writing on the potato-disease, says its prevention depends upon attention to three things: 1. The choice of seed. 2. The removal of mycelium and resting spores from the seed chosen, to be accomplished by drying in the sunlight, and by dipping the seed-potatoes in a solution of lime with a little carbolic acid; and 3. The preservation of seed in a temperature which will prevent the growth of mycelium. It will not grow in a temperature below 48° Fahr.

immense fields of sea-wrack which are found in the neighborhood of the Gulf Stream are estimated to cover a superficial area equal to that of France. M. Leps, of the French Navy, thinks that this sea-weed could be utilized for agricultural and industrial purposes, and suggests that it might be brought home in compressed bundles, or burned on the spot, and its soda and iodine thus secured.—American Journal of Science and Art.

cause is assigned, by M. Collas, for the blue color of the sky. In opposition to M. Lallemand, who attributes the color to a fluorescent phenomenon—a reduction of refrangibility in the actinic rays beyond the violet end of the spectrum—M. Collas maintains that the color is due to the presence of hydrated silica in a very finely-divided state, carried into the atmosphere with the aqueous vapor. The blue color of the Lake of Geneva is referred to a similar cause.—Athenaeum.

Australian meat preserving companies have commenced the exportation of bone-dust to England. By strong pressure, the crushed bones are moulded into briquets 6 inches square and 3 thick, weighing about 6 pounds. A ton weight of this compressed bone-dust occupies 26 cubic feet.

simple remedy for echo in large public halls, churches, and the like, is suggested by a writer in the Railway Times, viz., the stretching of thin wires. These break the waves of sound, and prevent reverberation.

London Times reports that Mr. Aden, indoor engineer in the Edinburgh Telegraph-Office, has invented a system by which, with existing instruments, it has been found practicable to send messages from both ends of a single wire simultaneously. The invention has been tested between Edinburgh and Glasgow, and it has been found that one wire is capable of doing double work.

manufacture of spirits from mosses and lichens is becoming an important branch of industry in Northern Russia. The alcohol is said to be of good quality. The development of this industry will have an important bearing on the question of food-supply in the Russian Empire; the more spirits made from Iceland moss, the more cereal grains will there be left to subsist the people.

the working-collier is provided with a safety-lamp, ingenuity must be further taxed to provide the means of guarding against his mad recklessness. The man will open the lamp, if it is at all possible, to get better light for his work, to light his pipe, or merely from foolhardiness. Lamps have, therefore, been contrived which go out on being opened. Another plan is to lock the lamp with a plug of lead, on which a device is punched, and which cannot be opened without breaking the plug. The latest contrivance is a lamp which is closed with a steel spring, and which cannot be opened except by the action of a very powerful magnet, such as the colliers would not be likely to possess.

is proposed in France to supersede gold and silver coinage by platinum. The use of this metal for coins is nothing new, for the Russian Empire had a platinum coinage over a quarter of a century ago. As early as 1799, experiments were made at the Paris Mint, and some beautiful specimens of platinum medals were produced.