246 Intelligence and Miscellaneous Articles. 



19. The same direction of vi- 19. To the colour A belong, 

 bration belongs to the colour A when the observation is in the 

 when the observation is in the direction of the axis, vibrations 

 direction of the axis or perpen- perpendicular to the axis. When 

 dicular to it. the observation is perpendicular 



to the axis, the vibrations are in 

 the direction of the axis and per- 

 pendicular to all those of the last 

 case. Yet there is no trace of 

 any action on the part of the first 

 set. 



20. For the same direction of 20. For the same direction of 

 vibration and the same wave- vibration there are different co- 

 length there is the same colour loursand therefore different wave- 

 throughout the whole crystal. lengths. 



The author concludes from this reasoning, that the assumption of 

 vibrations perpendicular to the plane of polarization leads to clear, 

 simple, consequent, and connected views of the whole subject ; while 

 the opposite supposition involves obscure, overloaded, and contra- 

 dictory representations. Similar arguments may be drawn from a 

 consideration of biaxial or trichromatic crystals. We must, how- 

 ever, refer to the original paper in Poggendorff's Annalen for October 

 1855, for a fuller exposition of the author's views and arguments. — 

 Silliman's Journal for January 1856. 



ON THE INCANDESCENCE OF METAL WIRES IN ALCOHOLIC 

 VAPOUR. BY H. REINSCH. 



Reinsch long since showed that wires of all the infusible metals, 

 as also most of the metallic oxides, continued incandescent in the 

 vapour of alcohol, so that this property is by no means peculiar to 

 platinum. He has had the opportunity of making some experiments 

 upon this phEenomenon, which have led him to a remarkable observa- 

 tion. When a spiral of copper wire is fastened in the manner 

 described by Reinsch upon the wick of a spirit-lamp, and the lamp 

 is lighted and then quickly blown out, the copper wire continues 

 incandescent just as well as platinum. This incandescence, however, 

 only lasts two to three minutes. But if a small fragment of coke be 

 inserted into the spiral and the whole be brought to a red heat, the 

 wire will continue to glow permanently after the extinction of the 

 flame. The author attempted to explain this phaenomenon by the 

 supposition that the high temperature was better maintained by the 

 fragment of coke, as it does. not carry off the heat so quickly as the 

 wire, and as it were forms a sponge, which always retains sufficient 

 heat to communicate to the wire the temperature necessary for its 

 incandescence. This supposition, however, was not confirmed, as the 

 spiral was not extinguished even when the piece of coke was removed. 



