Intelligence and Miscellaneous Articles. 



.19 



467 strong. 



504*5 strong. 



548 strong. 



470 



508-5 



554 



475 



515 



560 



479 



522 strong. 



564 



483 



526 strong. 



570 



487-5 



532 



577 



492 



538 



581 



498 



544 



590 



406 very broad and vague. 



418 the same. 



431*5 strong. 



434*5 strong. 



445 



448 strong. 



453-5 



462 



No hydrogen or nitrogen-band is visible. 



2. Spectrum in the flame of Hydrogen. — This I produced by press- 

 ing the hydrogen-flame, charged with traces of sulphurous acid, 

 against a layer of cold water falling vertically. The beautiful blue 

 light then produced is easily resolved by the prism into bands quite 

 similar to the preceding, but some of which are brighter than the 

 corresponding bands of the electric spectrum, so as at first sight to 

 present a somewhat different appearance. Their wave-lengths were : — 



396 very broad and vague. 



438-5 



471 strong. 



504 



404 the same. 



444*5 strong. 



476 



509 



408-5 vague. 



448 



479 



515 



416 



453*5 



483 



faint lines 



419 



457*5 



487-5 



as far as to 



427 strong. 



462 



492 



550 



431*5 strong. 



467 



498 strong. 





3. I examined by transparency a layer of sulphur vapour heated 

 to dull redness. When a very powerful light is employed, such as 

 that of magnesium, in the blue some black bands are perceived which 

 nearly correspond to the following wave-lengths : — 



471 465 462 very faint. 456 445 437 

 Here there may be some uncertainty, because magnesium furnishes 

 some lines in this portion of the spectrum ; nevertheless, as these 

 bands are only observed with sulphur, I think they are due to the 

 reversal of the preceding spectrum. 



All these results were obtained with a spectroscope with only one 

 prism, as the band spectra, unlike the line spectra, will not bear rnuch 

 dilatation ; therefore one cannot absolutely depend on the number 

 which expresses the millionths of a millimetre. 



I am pursuing the study of the band spectra of the metalloids, in 

 M. Wurtz's laboratory. — Comptes Rendus, 1871, No. 9. 





ON SOME LUMINOUS TUBES WITH EXTERIOR ELECTRODES. 

 NOTE BY M. ALVERGNIAT. 



The presence of metallic electrodes (which sometimes become 

 strongly heated) in Geissler tubes may occasion numerous miscon- 

 ceptions when the light is analyzed in the spectroscope. Those 

 electrodes absorb and emit gases, may cause cracks in the glass ; 

 and they partly volatilize, so as to tarnish the interior surface of the 

 latter. Now it is not necessary to place the electrodes inside the 

 tubes, since these can be charged by influence (as we have seen in 

 the preceding note) without their brightness being much diminished. 



Besides, the exterior electrode need not be a collar ; it may be 



