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THE POPULAR SCIENCE MONTHLY. 



Writing on the subject of malaria, Dr. 

 Re)' 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 au- 

 thorities in pronouncing cold, with damp, 

 to be exceedingly dangerous. Residents in 

 lowland or damp situations should, there- 

 fore, take special precautions to keep the 

 circulation in such a condition that the ex- 

 tremities are not cold, and the surface gen- 

 erally is comfortably warm. By maintain- 

 ing this condition of body, other diseases 

 besides the so-called malarial would also be 

 warded off. 



The 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 Ala- 

 bama. 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. 



A correspondent of the London Times, 

 writing on the potato-disease, says its pre- 

 vention depends upon attention to three 

 things : 1. The choice of seed. 2. The re- 

 moval of mycelium and resting spores from 

 the seed chosen, to be accomplished by dry- 

 ing 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. 



The 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 indus- 

 trial 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. 



A curious cause is assigned, by M. Col- 

 las, for the blue color of the sky. In oppo- 

 sition to M. Lallcmand, who attributes the 

 color to a fluorescent phenomenon a reduc- 

 tion of refrangibility in the actinic rays be- 

 yond 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. A thenceum. 



The Australian meat preserving com- 

 panies 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. 



A vert simple remedy for echo in large 

 public halls, churches, and the like, is sug- 

 gested by a writer in the Railway Times, 

 viz., the stretching of thin wires. These 

 break the waves of sound, and prevent re- 

 verberation. 



The London Times reports that Mr. 

 Aden, in-door 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 simulta- 

 neously. The invention has been tested 

 between Edinburgh and Glasgow, and it has 

 been found that one wire is capable of doing 

 double work. 



The manufacture of spirits from mosses 

 and lichens is becoming an important branch 

 of industry in Northern Russia. The al- 

 cohcl 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. 



When the working-collier is provided 

 with a safety-lamp, ingenuity must be fur- 

 ther 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 pow- 

 erful magnet, such as the colliers would not 

 be likely to possess. 



It 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 speci- 

 mens of platinum medals were produced. 



