M. Espenschied on Nitride of Selenium. 277 
(1) The mountain mass must not be considered as one rigid 
mass of rock without natural joints. The Himmalaya Moun- 
tains are far too irregular in their structure, and too full of gigantic 
eracks and joints in all directions to allow of our applying the 
principle of the arch in the way Professor Haughton suggests. 
Moreover, if the cross strain in his arch, of 500 miles span and 
thickness of only one quarter of a mile at the spring, is not suffi- 
cient to compress the materials of the rock, it will surely break 
off angles, as I have mentioned in art. 2, p. 346 of the paper 
alluded to, and a catastrophe would ensue. 
(2) If Professor Haughton will not admit this, and still thinks 
that the principles of the arch should be applied to the crust 
under the Himmalayas, what will he say to the second part of 
my paper, in which the upward effect of the ocean is considered ? 
Here the arch cannot possibly act. 
(3) Professor Haughton notices a mistake I made in omitting 
a 2 in my calculation; but he observes that, as it does not 
seriously affect my result, he lays no stress upon it. This mis- 
take (which also occurs, I fear, in a treatise on “ Attraction, 
Laplace’s Coefficients, and the Figure of the Earth,” which by 
this time is, I suppose, published) I detected about a month ago, 
when it was too late to correct it. The calculation, however, in 
which it occurs is not to find the actual thickness of the crust, 
as will be obvious to my readers, but only to show that it is very 
thick. Where the mistake occurs in your Journal, the result I 
bring out is that the thickness of the crust in the middle of the 
mass aud at the end is 581 and 576 miles; whereas if the mis- 
take had not occurred, it would have come out 581 and 570 
miles, which not only does not affect my conclusion regarding 
the great thickness seriously, but in fact not at all. 
Caleutta, January 21, 1860. 
XXXVII. Chemical Notices from Foreign Journals. By. AvK1N- 
son, Ph.D., F.C.S., Teacher of Physical Science in Cheltenham 
College. 
(Continued from p. 216.] 
SPENSCHIED*, in a recent dissertation, has described a 
compound of nitrogen and selenium obtained by the action of 
ammoniacal gas on sublimed chloride of selenium, SeCl*. The 
action is so very violent that the ammoniacal gas must be diluted 
with a large volume ef hydrogen, and the vessel in which the 
action takes place carefully cooled. The chloride gradually 
becomes green, and ultimately changes into a brown mass, in- 
* Liebig’s Annalen, January 1860. 
Phil. Mag. 8. 4. Vol. 19. No. 127. April 1860. U 
