416 Scientific Intelligence. 
on an achromatic lens in the principal focus of which is a plane 
mirror reflecting the image on to the same screen. The colors are 
the image appears curiously furrowed with inclined black bands. 
By simply turning a prism so as to illuminate the film with light 
d yap 
spectrum of the reflected beam is obtained, showing inclined dark 
bands across its breadth.—J. de Physique, ii, 409, Dec., 1873. 
G. F. 
i 
‘ , N,O,.—BuRTHELoT 
has recently published an improved process for obtaining readily 
are obtained, which are perfectl e. From 150 grams of nitric 
acid, nearly 80 grams of the ceestala were yaak This sub- 
stance is non-explosive, either as a solid or in vapor. It decom 
poses, however, very easily, and this at the ordinary temperature, 
as Deville has observed, into nitrogen tetroxide and oye It 
should not be preserved in hermetically sealed vessels. It keeps 
well in good glass stoppered bottles placed under a bell-glass with 
sulphuric acid. In the air the crystals evaporate slowly, ¢¥ olvin 
abundant vapors, but not liquefying. Hence they can weigh 
