298 Scientific Intelligence. 
the faces through which we shall see one of the axes must be 
found by trial. We succeed easily by employing an Amici’s mi- 
croscope ad are recompensed by the result, as crystals of — 
pane om cones twice as open as those of <r — 
Phys., i 
$2. ’Dieleo tric Capacity of Gases.—M. L. Seneeies a sie en- 
of 300 small Daniel cells being employe 
In the following table the first column 1 give s the name of the 
gas, the second the — root of the ‘iciprerie constant, and the 
third the a ie of refractio 
Jk. n. 
Air 35 F 000806 17000294 
Carbonic nidi«. rt ee keg 1°000473 17000449 
Hydrogen_..-.--..... .. 1000182 17000138 
Carboni¢ oxide.< oi... 1°000345 1000340 
Nytrowsoeidel.. (22. 22: 1:000497 17000503 
Olefians eae. focus 5. 2: 1:000656 1000678 
Marsh . Polya cuca . 19000472 a 
BAL Annal., 
The smal hod y ieeiired luminous by Phosphuretted Thy: 
drvigen —Dr. Gro. Maciean of Princeton, in a private communi- 
cation to the editors, says: 
sm veral years ago, after s Pay ie a portion of the day in ex 
attributed to it, nor was my health apparently in any Way 
fected by it. 
Probably a repetition of the trial would reproduce the results 
observed by Dr. Maclean, which have apparently escaped nolany 
heretofore because unsought. 
Il. Greotocy anp Natura HIsTory. 
i, Pseudomorphism and Meta san eae a correction ; bY 
James D. Dana.—In — notice of Mr, Hunt’s Essays in _ 
Journal, volume ix (the number for Feb., 1875), I say, on page 
109: “ With the exception of the year 1858, I have never he 
