SALMON — ItESEAUCIIES ON PHHUDOMOKI'llS. 
whicli compose the terrestrial crust contain but a small number of 
minerals * It seems even that certain minerals wei'o unable to form 
themselves without others being developed at the same time. Thus, 
when there are felspars in a rock, we also most usually find the 
micas, augite, or hornblende. Similarly it is rare for orthoclase to 
be met with, without quartz. The associations of minerals are be- 
sides observed as well in normal and in abnormal rocks. In addition, 
as has been shown by Messrs. Breithaupt, Henwood, and B. Cotta, 
the minerals have generally succeeded in the same order.f It can- 
not, therefore, be doubted that minerals manifest a great tendency to 
form constant associations. 
There is eminently one particular case in which the associations 
are very evident, and as intimate as possible ; it is when two minerals 
are crystallized in such a manner that the one envelopes the other : 
we then say that there is envelopment. 
Envelopment. 
The envelopment of minerals is well fitted to throw light on the 
conditions in which they were formed, and has conseqtiently attracted 
special attention. The older geologists occupied themselves with 
this subject, particularly Rome de I'lsle, De Boumon, Haiiy, Ger- 
hard, Gallois, Germar, Marx, Von Born, Werner, Karsten, Mohs, 
Chrichton, and Phillips. More recently, it has been noticed in 
diverse circumstances by Messrs. Breithaupt, TTaumann, G. Bischof, 
Haussmann, Haidinger, Scheerer, G. Rose, Sillem, Zippe, Von 
Zepharovitch, Tamnau, Wieser, Wiebye, A. Knop, Websky, Mar- 
bach, Genth, Liebener, Null, Levy, Durocher, Sir David Brewster, 
H. C. Sorby, Silliman, Alger, Nicol, Jackson. But it is particularly 
to Messrs. R. Blum, G. Leonhard, Kenngott, A. Seyffert, and 
Sochting, that we owe the pi'incipal labours on envelopment.^ 
When we regard the question in its widest generality, one mineral 
may envelope an almost indefinite number of other minerals ; the old 
popular maxim, " tout est dans tout," seems to be verified for the 
mineral kingdom. 
However, the number of minerals enveloping and enveloped is not 
so great as we might at first sight suppose ; indeed, they may be 
considerably reduced if we limit them to those which are well crys- 
tallized, and the most important. 
The following is a table which gives a resume of these, and shows 
us the envelopment of the principal minerals. The classification 
adopted is that of Mr. Dana (" System of Mineralogy"). The en- 
veloping mineral is given in the first column of the table, and the 
* On this subject see my paper " On Kocks." " Greologist," vol. ii., p.p. 49 
and 22.— H. C. S. 
t Breithaupt, " Paragenesis der Minerahen." Henwood, " Phil. Mag. :" 1846, 
p. 360. B. Cotta, " Erzlagerstatten :" 2nd ed., p. 72. 
X " Naturw. Verein in Halle," 1853, t. xi. : 6 Hollandische Societat der Wis- 
senschaften zu Haarlem : 1854. 
