Open main menu

Page:Popular Science Monthly Volume 25.djvu/734

This page has been validated.
718
THE POPULAR SCIENCE MONTHLY.

tice. Mr. Fleuss has also, in conjunction with Mr. Foster, produced a safety mining-lamp which depends for its vitality on principles similar to those of the breathing apparatus, and is equally useful and safe under water and in the most dangerous gases. It is essentially a lime-light, ignited by the burning of methylated spirits instead of hydrogen gas, and securely guarded against contact with the outer air. It will burn for four hours equally well under water, in carbonic acid, or in fire-damp, and it can not get hotter than boiling water. Its usefulness, says "Iron," "we have seen demonstrated by a diver at the Fisheries Exhibition, who, equipped with the breathing apparatus, and having a Fleuss lamp, remained for long periods under water, both man and lamp being wholly cut off from the outer atmosphere during the periods of immersion. In like manner we have seen the respiratory apparatus put to the test by a man equipped with it remaining for some time in an air-tight iron chamber filled with dense smoke and noxious vapors. But above and beyond this is the experience which has been gained from its use in actual practice, notably in the case of the flooding of the Severn Tunnel, as regards subaqueous work, and in the cases of the Seahara and Killingworth collieries with respect to coal-mine accidents." In the case of the explosion at the Lycet collieries, in which several lives were lost, an early exploration, which in ordinary circumstances would have been impossible, was safely effected by means of the Fleuss apparatus.

 

The Army-Worm.—Several caterpillars have been popularly but inaccurately called the army-worm; but, according to the recently published pamphlet by Professor Riley on the subject, the real worm which is so destructive to growing grass and grain is the Leucania unipunctata, a species that has a very wide range on this Continent. The worm is the larva of a moth about an inch and a half in wing-expansion, and of a reddish-gray color, which lays its eggs in wild or cultivated grass, or in grain, along the inner base of the terminal blades, where they are yet doubled, or between the stalk and its surrounding sheath, or even in the cut straw of old stacks, or in corn-stalks. The larvæ feed for a time after hatching in the fold of the leaf, which they so resemble in color as usually to escape observation. They are stationary in habit so long as they have sufficient feed, but take up the march when their pasture is exhausted; and in those seasons when they have been multiplied to excess they constitute a veritable army marching in solid rank. Their occasional sudden appearance in vast numbers over large stretches of territory is one of the phenomenal features of their life; but it is not so wonderful a fact, after all. They are nearly always with us in greater or less numbers, and if the season is a dry one they multiply prodigiously. An immense crop of moths is accordingly produced, and then, each one of them laying seven or eight hundred eggs, stock the fields and pastures in profusion, depositing the eggs for the immense host which is to appear in the following year. In confirmation of this view, examinations of the weather records show that the years preceding army-worm years have been universally characterized by drought. Three broods of them may be produced in a year. Their natural enemies are not less than fourteen species of birds, a metapodious bug, and numerous parasites. The usually applied remedies look to the wholesale destruction of the worms or the eggs. Among them are burning the old grass, preferably as late as possible in the spring; digging a ditch to serve as a trap into which they will fall on their march, after which they may be destroyed in various ways—mashing them in the field with heavy rollers, and dragging a rope across the field to crush them. Thin tillage is also a preventive, by causing the worms to be exposed to the sun.

 

What destroyed Casamicciola?—Professor Palmieri, of the Mount Vesuvius Observatory, believes that the destruction of Casamicciola, in Ischia, was not the immediate effect of the earthquake, but was caused by a caving in of the ground under the city, which might, perhaps, have been precipitated by an earthquake-shock. The trachytic rocks on which the town is built rest upon a bed of clay, in which extensive galleries have been dug in the course of centuries, while the clay has been mined for industrial purposes. As early as 1837,