+ 
174 General Notes. [Feb. 
of molten material which flowed out upon a land surface and 
there cooled, no matter in what geological period, always pos- 
sesses characteristics which distinguish it from a mass of the 
tance below the surface. It is probable that rocks of the latter 
class have been formed throughout all time since the beginning 
of the Laurentian, and may be in process of formation at present, 
but at such depths that we can never hope to see them. at most 
of the plutonic rocks with which we have to deal were really 
formed early in the earth’s history, is due merely to the fact that 
that portion of the earth’s crust in which they are found has 
been eroded to such an extent as to lay bare its innermost 
depths. > 
In the new volume under consideration, Rosenbusch character- 
izes these deeply-formed rocks as possessing, I., each of their 
constituents in but one generation, and, II., so developed that 
the different individuals have mutually interfered with each 
other’s growth, thus giving rise to the granular (kdrnige) struc- 
ture. When none of the constituents possess crystal outlines, 
the structure is cated hypidiomorphic ; when certain of the con- 
quently possess this granular structure, are designated as intrusive 
_ or plutonic (Tiefengesteine). 
The intrusive rocks are subdivided in accordance with their 
chemical and mineralogical composition into granites, syenites, 
_eleolite syenites, diorites, gabbros and norites, diabases, theralites, 
and peridotites. All these are characterized by the possession of 
the hy pidtomorphic structure, in which by far the larger part of 
the constituents are allotriomorphic (possess a form due to ex- 
ternal causes and not to the action of intermolecular forces,—z.., 
words, s 
constituents become zdiomorphic (possess eyil outlines), and 
the rock tends to the Forala structure, such as many of 
the diabases. 
On glancing over the list of the names of intrusive rocks, it 
will be noticed that in it are included, with the single exception 
of teschnite, all those formerly described as pre-Tertiary with a 
granular — In the place of teschnite we find the new te 
sie theral 
The abolition of the old type teschnite is due particularly to 
= work we Sne, a in 1885, after a paana examina- 
lity thin his 
