158 Scientific Intelligence. 



monoxide and ethylene about — 150°, and air a minimum temper- 

 ature of —210° to — 213°. These low temperatures were meas- 

 ured with a dry hydrogen thermometer, or by alcohol or ether 

 thermometers, verified by the hydrogen thermometer. The 

 author observes that the very long radiant waves emitted at 

 these very low temperatures pass readily through, almost all 

 bodies. Thus a vessel at —110° for example will cool with prac- 

 tically the same rapidity whether the layer of cotton enveloping 

 it be 50 cm or 10 cm or only 2 cm in thickness. Moreover, he finds 

 that when chloroform is immersed in nitrogen monoxide at 

 — 120°, a thermometer placed in it sinks to — 68 - 5° and crystal- 

 lization begins. If transferred to a mixture of carbon dioxide 

 and sulphur dioxide at —80°, the thermometer falls to —80° and 

 the crystals of chloroform melt again. Replaced in the nitrogen 

 monoxide at —120°, the thermometer rises to — 68'5° and crys- 

 tallization begins again. At — 83 '5° the crystals remain station- 

 ary increasing when the temperature falls and melting when it 

 rises. Since crystallization takes place on the inner wall when 

 the vessel is cooled at — 120° it seems probable that the thermom- 

 eter in the middle is affected by the heat of crystallization and at 

 — 68*5° is in dynamic equilibrium with the medium in which it is 

 immersed. At —80° no crystals are formed and the thermom- 

 eter is affected by radiation only. — C. H., cxiv, 1245 ; J. Chem. 

 Soc, Ixii, 1138, October, 1892. G. r. b. 



6. The new Telephotographic lens. — This invention of T. R. 

 Dali/ueyer makes it possible to obtain large pictures of objects 

 situated at long distances by short exposures. The anterior 

 element of his combination of lenses is a positive lens of lnrge 

 aperture and short focus, while the posterior is a negative and of 

 fractional part of the focal length of the former lens. One is 

 reminded of the principle of the Galilean telescope, with this 

 difference, that the emergent rays are convergent and not diver- 

 gent. The size of an image thrown on a screen can be varied at 

 will by altering the distance between the elements. The farther 

 the lens is from the focussing screen the longer will be the time 

 of exposure. Some pictures taken by this lens were exhibited at 

 a meeting of the Camera Club in London. One picture represented 

 a building at a distance of 500 yards. The telephotographic 

 lens, with 30 inches extension, represented the house as 6^ inches 

 long, while a rapid rectilinear lens, with extension of 14 inches, 

 gave the house as f inch long. — Nature, p. 161, Dec. 15, 1892. 



J. T. 



7. Oxygen for lime light. — The oxygen gas obtained from 

 atmospheric air by what is known as the Brin process, gives on 

 an average a purity of 95 per cent oxygen. T. C. Hepworth in 

 a letter to Nature, has compared the performance of this gas in a 

 lime light with an impure gas containing only 60*6 per cent oxy- 

 gen. The light afforded by the impure oxygen was about one- 

 half as intense as the light given by the purer oxygen. With 

 the good oxygen the lime cylinder was quickly fitted, while with 



