568 
ELEMENTS OF GEOLOGY. 
chain. This protrusion of No. I. has been caused by the ig¬ 
neous agency which produced the newer plutonic rocks Nos. 
11., III., and IV. Part of the primary fossiliferous strata. No. 
1., have also been raised to the surface by the same gradual 
process. It will be observed that the Recent strata No. 4 
and the Recent granite or plutonic rock No. IV. are the most 
remote from each other in position, although of contempora¬ 
neous date. According to this hypothesis, the convulsions 
of many periods will be required before Recent or Post-ter¬ 
tiary granite will be upraised so as to form the highest 
ridges and central axes of mountain-chains. During that 
time the Recent strata No. 4 might be covered by a great 
many newer sedimentary formations. 
Miocene Plutonic Rocks. —A considerable mass of syenite, 
in the Isle of Skye, is described by Dr. MacCulloch as inter¬ 
secting limestone and shale, which are of the age of the lias. 
The limestone, which at a greater distance from the granite 
contains shells, exhibits no traces of them near its junction, 
where it has been converted into a pure crystalline marble.^ 
MacCulloch pointed out that the syenite here, as in Raasay, 
was newer than the secondary rocks, and Mr. Geikie has since 
shown that there is a strong probability that this plutonic 
rock may be of Miocene age, because a similar Syenite hav¬ 
ing a true granitic character in its crystallization has modi¬ 
fied the Tertiary volcanic rocks of Ben More, in Mull, some 
of which have undergone considerable metamorphism. 
Eocene Plutonic Rocks. —In a former part of this volume 
(p. 277), the great nummulitic formation of the Alps and 
Pyrenees was referred to the Eocene period, and it folio\vs 
that vast movements which have raised those fossiliferous 
rocks from the level of the sea to the height of more than 
10,000 feet above its level have taken place since the com¬ 
mencement of the Tertiary epoch. Here, therefore, if any¬ 
where, we might expect to find hypogene formations of Eo¬ 
cene date breaking out in the central axis ‘or most disturbed 
region of the loftiest chain in Europe. Accordingly, in the 
Swiss Alps, even thej^scA, or upper portion of the nummu¬ 
litic series, has been occasionally invaded by plutonic rocks, 
and converted into crystalline schists of the hypogene class. 
There can be little doubt that even the talcose^ granite or 
gneiss of Mont Blanc itself has been in a fused or pasty state 
since %\\^flysch was deposited at the bottom of the sea; and 
the question as to its age is not so much whether it be a sec¬ 
ondary or tertiary granite or gneiss, as whether it should be 
assigned to the Eocene or Miocene epoch. 
* “ Western Islands,” vol. i,, p. 330. 
