J82 



THE POPULAR SCIENCE MONTHLY. 



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 con- 

 siderable 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 indepen- 

 dent 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 bus- 

 tard, and one or two smaller birds. A wild 

 cow, or white antelope, related to the Af- 

 rican 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 com- 

 mon 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. 



Inseet-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 princi- 

 pal 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 depre- 

 ciation. They may be used with much ef- 

 fect against house-flies simply by charging 

 the room with the dust. Mr. William Saun- 

 ders 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 dis- 

 abled; they seem, however, to be only stu- 

 pefied, 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 fire- 

 damp 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. Gran- 

 ville Cole, Ph. D., recently described be- 

 fore the British Society of Arts a new me- 

 tallic compound which possesses some re- 

 markable and valuable qualities. Its prep- 

 aration 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, pos- 

 sessing great tenacity, and having a pecu- 

 liar 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 sul- 

 phur sulphides. The compound has the ad- 

 vantages of a low melting-point, 320 Fahr., 



