REPORT ON GEOLOGY. 
379 
subsequent to the consolidation of the latter rock,) presents a 
fact of great importance, in as much as it clearly evinces that the 
adjoining primitive chains of mountains must have been subject 
at the least to two asras of disturbance ; the first when the injec¬ 
tion of the granitic mass, yet in a fluid state, rent the incum¬ 
bent micaceous slates, injecting veins of its substance into their 
fissures*; and a second at a much later period, subsequent not 
only to the refrigeration of the granite, hut even to the deposi¬ 
tion of the Brora oolites, which partook in the motions occa¬ 
sioned by this latter elevation, and have been in places shattered 
by this convulsion into fragments which have been reunited into 
a brecciated conglomerate. 
The next geological group which requires our notice beneath 
the lias and oolites, is that which is universally characterized 
by the new red or variegated sandstone, the gres bigarre of 
the French, and hunter- sandstein of the Germans, which is 
associated in its lower portion with the magnesian lime or 
zechstein, and (on the Continent) in its upper part with the 
muschelkalk and keuper. Geology stands much in need of a 
convenient name for this group; and I will venture therefore to 
propose the term Poecilite (from the Greek Troixihog), as express¬ 
ing its characteristic rock the gres bigarre, and hence denomi¬ 
nate the group, pcecilitic. Rrongniart has already adopted the 
Gallicised form Pcecilien. 
The elaborate Memoir of Prof. Sedgwick on the Magnesian 
Limestone of the Northern Counties is doubly valuable as show¬ 
ing at once the variations and also the identities presented by the 
comparative view of the same formation in distant points ; while 
in our southern counties this formation exists only in the form of 
a conglomerate, derived from the debris of the older carbonifer¬ 
ous lime united by a dolomitic paste, thus illustrating the original 
mode of its formation ; in the northern counties it becomes fully 
developed in a regular series of calcareous beds, distinguished by 
peculiar organic remains, exactly corresponding with the zech¬ 
stein and raucliwacke of the contemporaneous German deposits; 
w hile the organic remains contained are very important as form¬ 
ing a link between the types of the older subcarboniferous and 
successive newer rocks. Prof. Sedgwick has well shown how, if 
we take into account the intermediate formations of muschelkalk 
and zechstein, so amply developed in Germany, but not yet dis¬ 
covered in these islands, we may trace a regular graduation in the 
* I believe, indeed, that at the Ord of Caithness, where the granite is in contact 
with the oolite, the mica slate is absent; but there is surely no reason to believe 
this particular granitic mass different in age from the other granites of the same 
portion of the Highlands, which are thus related to the mica slates. 
