406 Intelligence and Miscellaneous Articles. 



which is no exaggeration, we arrive at divergences of the order of 

 magnitude of the deviations found ; it is therefore impossible to 

 pronounce a decision upon either the direction or even the existence 

 of those deviations. All that we can say is that at the lowest pres- 

 sures at which experiments have been made(l inillim. or even less ; 

 I have experimented at two tenths of a millimetre) no abrupt 

 change in the law of the compressibility of gases appears to be pro- 

 duced ; they still follow Mariotte's law, with the exception of diver- 

 gences for which the experiments cannot be responsible. It is 

 certainly possible that sufficient rarefaction, acting like a great 

 elevation of temperature, would cause other gases to follow the 

 law jp(«— a)=c, as takes place for hydrogen ; but there is a great 

 distance from this to the boundary state spoken of by Mendeleef 

 and Siljerstrom, in which the gases would become infinitely little 

 compressible — a mere hypothesis, to which the numerical results 

 of M. Siljerstrom do not even appear to lead, as M. Petier has 

 already remarked in the Journal de Physique. 



The study of carbonic acid has led me to analogous conclusions. 

 For hydrogen the deviations found have varied between — 0*0010 

 and 0*0028 for initial pressures between 3 and 6 inillim. in round 

 numbers. — Camples Bendus do V Academic des Sciences, Aug. 7,1882, 

 t. xcv. pp. 281-284. 



ON THE INFLUENCE OF TEMPERATURE UPON THE SPECTRA OF 

 METALLOIDS. BY M. D. VAN MONCKHOYEN. 



Kirchhoff and Bunsen have shown that the temperature of the 

 flame in which a substance is reduced to vapour has no influence 

 upon the position of the bright lines of its spectrum. When, for 

 instance, sodium or lithium is volatilized in the flame of a spirit- 

 lamp, or in that of the oxyhydrogen blowpipe, the lines remain the 

 same, but their brilliancy increases with the temperature : most 

 frequently some new thin lines appear at the elevated temperatures ; 

 but it never happens that those which have already been emitted 

 at lower temperatures disappear. If this is always the case as 

 regards the metallic vapours, it is never so with the lines emitted 

 by the metalloids *. Flacker has in fact shown that oxygen, ni- 

 trogen, sulphur, selenium, &c. give two different spectra which 

 have no line in common, according as the spectral tubes contain- 

 ing these substances are heated by the ordinary spark of the elec- 

 trical machine or by that of a Leyden jar. He admits there- 

 fore, and with him nearly every physicist, that certain elementary 

 bodies give, at a high temperature (Leyden jar), a spectrum different 

 from that given by the same body at a low temperature (ordinary 

 spark). 



But numerous and varied experiments have proved that we 

 can obtain those spectra called those of high temperature at very 



* Hydrogen is an exception ; hut this gas is known to be «a true 

 metal, not only as to its chemical properties, but also as to its physical. 

 Hydrogen bears, as regards conductivity of heat and electricity, the same 

 relation to other gases as mercury to the other liquids. 



