224 Mr Anderson’s Corrections for the Effects of Humidity 
rally, however, the edges are rounded off, and the faces of crys- 
tallisation in consequence curved, so as finally to obliterate the 
regular form altogether. The colour varies from a pale greenish- 
white, through several shades of mountain-green and verdigris- 
green, to a fine sky-blue. The hardness is — 5.5 to 6.0 of the 
scale of Mohs, between apatite and felspar, much nearer the 
latter, from which it can be scarcely distinguished. It agrees 
with the hardness of sodalite. Also the specific gravity, which 
in the present instance is far more important, agrees with that 
of sodalite, having been found in a detached crystal, which had 
a little grey felspar adhering to it, equal to 2.349, while the 
specific gravity of the Greenland variety of sodalite is = 2.29 5. 
The blue varieties of this mineral are generally considered as 
Haiiyne. 
The comparison of these varieties is intimately connected with the 
question, which has been sometimes discussed, Whether Sodalite, 
Spinellane, Haiiyne, and the crystallised Lapis lazuli, really pos- 
sess characters sufficiently marked, to induce us to consider them 
as distinct species ? I regret that I have not had an opportunity 
of consulting Mr Breithaupt’s observations in this respect, who 
has been at much trouble in ascertaining some of the properties 
of the minerals above mentioned ; but I had much pleasure in 
finding that Mr Bergemann, Professor Noggerath, and Mr Yon 
Gerolt, in an excellent memoir on this subject *, are of opinion 
that these substances, particularly the Haiiyne, and the Spinel- 
lane, or Noseane, from the lake of Laach, form varieties of one 
and the same species, as is there demonstrated by an accurate 
investigation of all the properties of a very complete collection 
of these minerals. 
Art. IV. — New Corrections for the Effects of Humidity on the 
Formula for measuring Heights by the Barometer. By 
Adam Anderson, A. M. F. R. S.E., Rector of the Aca- 
demy of Perth. Continued from Vol. XII. p. 260. 
The results of a great variety of other observations, to deter- 
mine the elasticity and relative tension of atmospheric vapour. 
Noggerath’s Gebirge in Rheinland-Westphalen, vol. ii. p. 302. 
