Page:Popular Science Monthly Volume 17.djvu/294

282 sand-mound at the western edge of the hole. As seen from the tops of the higher rocks, the fuljes "run in long, sinuous strings with a main direction generally corresponding with their aspect," which gives them still more the appearance of huge horse-tracks. This desert is provided with a vegetation of its own, and is well clothed in the hollows and most of the plain with shrubs. The plants include three grasses and "two considerable shrubs, almost worthy to be ranked as trees." The ghatha, growing sometimes to the height of twelve or fifteen feet, gives a bright, smokeless flame, and makes the purest charcoal in the world. The Bedouin tribes make their summer home here, living on the milk of their camels, and independent of water, and always finding pasture. Among the wild animals are the ostrich, hares, the ibex, the leopard, a marmot, snakes, lizards, hawks, buzzards, the bustard, and one or two smaller birds. A wild cow, or white antelope, related to the African antelopes, is native to the region. Tracks of this animal were seen at least a hundred miles from any place where it could have procured water, confirming the assertion that it never drinks. Of insects, the dragon-fly, beetles, ants, and the common house-fly were noticed. A specimen of the painted lady butterfly, famous for its long flights, was seen sunning itself on the rocks of Aalem. This insect could not have been bred at any nearer point than the hills of Syria, four hundred miles off.

Insect-Powders as Remedies for Flies and the Aphis.—The insect-powders commonly sold are the powdered flowers of different species of Pyrethrum. Of the two principal kinds, which are known as the Persian and the Dalmatian powders, the Dalmatian is the more energetic. The flowers, whether whole or powdered, preserve their activity for a long period. Samples, which have been kept for six months, show no depreciation. They may be used with much effect against house-flies simply by charging the room with the dust. Mr. William Saunders says, in the "Canadian Entomologist," that he has frequently, after having charged the air in his kitchen and dining-room at night, found all the flies lying dead on the floor in the morning. Few will escape when the room is closed for half an hour after using the powder. Mr. Saunders has also applied the powder with excellent success to the destruction of the green aphis in his greenhouses. The pests will fall to the ground when the dust is blown among the plants, and in the course of an hour or two the greater part of them will be found disabled; they seem, however, to be only stupefied, not killed, as the flies are, and must be taken care of. The powder gives a more convenient and pleasant remedy than any other that we have. It is, moreover, safe.

The Damposcope.—Professor Forbes has invented an instrument for detecting firedamp and determining the quantity of light carburetted hydrogen in the air, which he calls the "damposcope." Its construction is very simple. Over the mouth of a straight brass tube is fixed a tuning-fork; inside the brass tube slides another tube of the same metal, which is moved by a regulating screw, so that the compound tube can be lengthened or shortened at will, and this movement is registered on a dial. To ascertain the amount of fire-damp in the pit, the instrument is taken to the suspected spot, the tuning-fork is set vibrating, and the screw is turned until the maximum sound is emitted. The index is then read off. It appears that the quantity of gas can be determined to within one half per cent.

A New Metallic Compound.—Mr. Granville Cole, Ph. D., recently described before the British Society of Arts a new metallic compound which possesses some remarkable and valuable qualities. Its preparation is based on the principle that the sulphides of metals combined with molten sulphur form a liquid, which, on cooling, becomes a solid homogeneous mass, possessing great tenacity, and having a peculiar dark gray—almost black—color. Nearly all the metallic sulphides will form, with an excess of sulphur, combinations which have the same properties. The combination used by Dr. Cole in illustrating his address was formed of an ore of iron pyrites containing lead and zinc sulphides. It belongs to the class of compounds known as thiates, or sulphur sulphides. The compound has the advantages of a low melting-point, 320° Fahr.,