Page:Popular Science Monthly Volume 26.djvu/737

Rh Testing Lighthouse-Lights.—Experiments have been begun by the corporation of Trinity House, at the South Foreland, England, to determine the relative value of the electric, gas, and oil lights as illuminants for lighthouses. The two lighthouses already established on the Foreland are illuminated by electricity, and are known as the high light and the low light. Near them have been erected three experimental light-houses: one, provided with electrical lights that have a total power of 30,000 candles; a second, furnished with gas-burners, of Mr. Wigham's design, that may give a total of 12,000 candles; and the third, with the oil and gas burners invented by Sir James Douglass. Three stations have been fixed for testing the lights, at distances respectively of half a mile, a mile and a quarter, and two and a half miles, at which huts have been fitted up as photometric observatories. Measurements will be taken for determining the penetrative power of the several illuminants in different states of the weather, and for ascertaining to what extent the principle of superposition of lights may be applied. One of the questions to be determined is relative to the comparative value of a large area of low illumination and a small area of high illumination.

New Pests in exchange for Old.—The Australasian colonies have suffered greatly from the multiplication of rabbits, which were originally introduced there from England. Now, they are crying out against a plague of dogs, which, increasing rapidly, and semi-wild, have become very destructive to the sheep, and rewards are offered for their destruction. It is proposed to import stoats and weasels into New Zealand to put down the rabbits; but, if this is done, there is danger that the latter estate of the colony will be worse than the present one. The sugar-planters of Jamaica have suffered greatly from the depredations of rats among their canes, and mongooses have been imported to destroy them, with apparent general benefit so far. "But the new importation continues to multiply and spread, not only on sugar-estates, but on the highest mountains, as well as along shore, even amid swamps and lagoons; and, when the sugar-cane rat is wholly exterminated, the mongoose will still go on increasing, and what then? Must the colonists find something else to exterminate the mongoose, and save their poultry, and so on ad infinitum?" As it is, many of the harmless indigenous fauna of the island are already diminishing under its attacks.



of the observatory at Cordoba, Argentine Republic, writes to Professor J. D. Dana that, after fourteen years of absence from his country, he finds himself so near the end of the special work on which he has been engaged that he hopes to revisit New England in the spring. Four volumes of star positions have been published, and a meteorological volume is started on its way. lie hopes to leave a mass of similar material for the occupation of his successors in the institutions; to leave the manuscript of seven astronomical quartos ready for the press; and to bring with him for publication in the northern hemisphere the "General Catalogue of Southern Stars," which will complete the astronomical work.

of Normanton, England, has invented a simple apparatus for detecting fire-damp in collieries. It consists of a small India-rubber hand-ball fitted with a protected tube. By compressing the ball and then allowing it to expand in a suspected atmosphere, it becomes filled with the air. It can then be taken to a safe place, and the air can be tested in a lamp.

is claimed to have attended the operation of the system of jetties planted by Captain Eads for deepening the channel of the Mississippi River near its mouth. While there were formerly only from eight to thirteen feet of water over the bars at low water, the least depth through the jetties was, last May, thirty-three feet, and the channel is steadily wearing itself deeper.

the recent meeting of the German naturalists and physicians at Magdeburg, Professor Landois, of Münster, spoke of the imperfections and comparative uselessness of most zoölogical gardens, and advised the institution of smaller gardens having well-defined fields of observation and investigation, lie cited the successful example of the zoological section of Westphalia and Lippe, whose garden of native beasts yielded an annual surplus. In connection with this is established a zoölogical museum of the district, in which the biological side is kept prominent, and which is nearly complete in invertebrates. The section publishes scientific lists of the native fauna, and is preparing for a wider circulation a "Westphalian 