Chap. VIIL] 
BRITISH SILURIAN ROCKS. 
183 
support the views respecting metamorphism derived from a survey of the 
Connemara tract, and which, after the proofs of an Upper Silurian series 
obtained in the Dingle district, seem to be rendered still more probable. 
May not, indeed, this view of the metamorphism of Lower Silurian rocks 
be applied to some of the crystalline rocks of Donegal ? and may they not 
eventually be brought into connexion with the true Lower Silurian oasis 
of Fermanagh and Tyrone ? This is a task worthy of the Irish Govern- 
ment Surveyors, and which, I have no doubt, they will ably accomplish. No 
one who has examined the small patch near Pomeroy could imagine, from the 
aspect of the schists, that it would have proved so highly fossiliferous as it 
did under the scrutiny of the lamented General Portlock. Hence we need not 
despair of finding the occupants of other former burying-places in various 
parts of the large area of Ireland over which Silurian rocks are believed 
to extend, though these deposits, being to so great an extent metamor- 
phosed, are necessarily sterile in organic remains. 
Some of the most characteristic of the Irish Silurian fossils will be 
noticed in the two ensuing chapters ; but a full acquaintance with them 
must be sought for in the works of Portlock and M'Coy, and in the tables 
of Sir Richard Griffith's map. 
Note. — Mr. Jukes has forwarded to me a description of a band of anthracitic 
coal, which occurs in ancient clay-slate and hard grits at Kilnaleck in the county 
of Cavan, and to which my attention was formerly directed by Mr. Kelly (see 
Appendix to first edition, p. 493). The strata in which this anthracite lies ex- 
tend from Cavan through the counties of Louth, Monaghan, Armagh, and Down ; 
and, from their composition as well as from their strike to the N.E., they are 
supposed to be of the same age as the anthracitic Lower Silurian schists of 
Dumfriesshire in Scotland already described (p. 152). This course of Irish 
anthracite, which varies in thickness from 1 to 12 feet (ranging, in a nearly ver- 
tical position, with its associated beds, from S.W. to N.E.), is a fuel of better 
quality (in short, a real coal) as well as of larger dimensions than any similar 
substance hitherto noticed in the Silurian rocks. 
Review of the Silurian Rocks of the British Isles. — In concluding these 
observations on the Silurian rocks of Britain, let me specially call the at- 
tention of the reader to the direct bearing which the discovery of Lower 
Silurian fossils in Sutherland must have in determining the true geological 
age of a very large portion of the stratified crystalline rocks of the western 
and central Highlands. 
It is, indeed, gratifying to me to find that my original theoretical view, 
repeated in previous editions of this work, seems now to be fully sus- 
tained — viz. that the great mountainous expanses of argillaceous, chloritic, 
micaceous, and gneissic schists, with intercalated quartz-rocks, marble, 
and limestones, which constitute the chief portion of the so-called pri- 
mary rocks of the west of Scotland, and extend from Dumbartonshire, 
through Argyllshire and Inverness- shire, into the central and eastern parts 
