» 
Mineralogy and Geology. 271 
the labors of pean Haidinger, and especially G. Rose, have been 
brought under a regular law, the subject bas not been exhausted. The 
He has 
many new planes, stati the number of sera rhombobedrons 
trom 13 to 60, and of plagihedral planes from 23 10 66. In the rhom- 
bohedral series, he finds only 17 which coexist with the corresponding 
inverse rhombohedron ; and in x plagihedral series, only 8, that have 
* 
preponder: of the regular Apt js shown. to, be. in a gyal Py 
State, paring the a of external perturbative influences. The 
among the more commo ms. M. Descloizeaux has given his 
measurements of these exceptional cases without disguising the discord- 
ances between calculation and measurements. 
The pretentions, now common with regard to the absolute exactness 
of crystallographic shea, leading to - use of the method 
least squares for estimating the probable errors, are a pure i Ho: sion, — 
is easy to show that artificial crystals are pate in angle by extraneous 
causes, foreign to the molecular forces ; and it is bo pang that natural 
crystals should have escaped like. influences. Whe number o 
inutes is somewhat uncertain, ites not reasonable Aa fea so much 
value to seconds: a number is reached ; en anomalies are 
8 grea 
to ascertain the limits of variation, and not blindly to assume an illusory 
coincidence in accordance with the abstract law o! 
he uew faces d ined by M. Descloizeaux have much i ine 
thus far ibe ee ute ci usion, and york suggest 
Some probable inductions. 
loizeaux next takes up the macles of quartz. He shows 
ca 
that the physical laws express only the limits of stable equilibrium 
