476 SCIENTIFIC RECORD FOR 1882. 



cial devices to collect and use the liquid ethylene are necessary, which 

 are described in the paper. {Comptes Rendus, May, xciv, p. 1224.) 



Demar9ay has studied the volatility of metals at low temperatures 

 in a vacuum. The metal was placed in a glass tube 12°"" in diame- 

 ter, closed at one end, and heated in a bath of the vapor of sulphur, 

 mercury, methyl sebate, aniline, methyl oxalate or water, giving tem- 

 peratures of 440O, 300°, 2920, 184°, 101°, and 100° respectively. A 

 thin U tube of glass was placed inside the first, passing to within two 

 centimeters of the metal, and kept cold by a current of water. The 

 space containing the metal was exhausted by a Springel pump. In a 

 longer or shorter time after the heating begins, a black deposit appears 

 on the bend of the U tube, which soon becomes metallic. Cadmium, 

 zinc, antimony, bismuth, lead, and tin were thus examined, and it was 

 found that they were volatile, cadmium at 100°, zinc at 184°, antimony 

 and bismuth at 292°, lead and tin at 300°. When the experiment con- 

 tinued for 24 or 48 hours, the deposit was considerable enough to be 

 weighed, being 5 to 15 milligrams. Cadmium at 184° gave in 20 hours 

 a deposit weighing nearly 10 centigrams. ( Comptes Rendus^ July, xcv, 

 p. 183.) 



Konowaloff has investigated the tensions produced by the vapors of 

 mixed liquids, including those which are miscible in all proportions as 

 well as those which are only partially soluble the one in the other. 

 {Wied. Ann., V, xiv, pp. 34, 219; J. Phys., April, II, i, p. 188.) 



Chistoni has given a historic sketch of the different theories of dew. 

 In his opinion the most efQcient cause of the production of dew is the 

 evaporation from the surface of the ground, which has been super- 

 heated during the day and the temperature of which Is maintained dur- 

 ing the night above that of the air. After a longer or shorter time, of 

 €Ourse this air becomes saturated. Contrary to the general impression, 

 nocturnal radiation plays only a secondary part in the phenomenon. 

 {II JSfuovo Cimento, III, x, p. 58; J. Phys., December, II, i, p. 566.) 



Troost has given a method for determining vapor densities at high 

 temperatures in glass by using for the purpose a bath of selenium 

 vapor, which boils at 665°. The glass must be difiBcultly fusible, the 

 capacity of the balloons being about 300 c. c. The author obtained for 

 the density of mercuric chloride thus determined 9.37 ; theory requiring 

 9.38. For iodine, 8.57 and 8.53 were obtained, showing that its expan- 

 sion coefficient does not differ from that of air, while its compression 

 coefficient at 440° is notably different, and at this temperature the den- 

 sity diminishes with the pressure from 8.7 to 7.35. Suli)hur vapor gave 

 2.94 and 2.92, while at 440° it is 6.6, and at very high temperatures it 

 is 2.2, showing a gradual decomposition like ozone. {Comptes Rendus, 

 June, xcv, p. 30.) 



Wiedemann has described a new form of apparatus for illustrating 

 geyser phenomena. It consists of a globe of glass of halt a liter capac- 

 ity, surmounted by two tubes, one a centimeter in diameter and 70 



