430 
THE GEOLOGIST. 
Commencing with the oldest strata, I may now assume, from the examina- 
tion of several associates on whose powers of observation as well as my own I 
rely, that what I asserted at the Aberdeen meeting, in 1859, as the result of 
several surveys, and what I first put forth at the Glasgow meeting of 1855, is 
substantially true. The stratified gneiss of the north-west coast of the High- 
lands, and of the large island of Lewis and the outer Hebrides, is the funda- 
mental rock of the British Isles, and the precise equivalent of the Laurentian 
system of Canada, as described by Sir W. Logan. Tlie establishment of this 
order, which is so clearly exhibited in great natural sections on the west coast 
of Sunderland and Ross, is of great importance in giving to the science we 
cultivate a lower datum-line than we previously possessed, as first propounded 
by myself before the British Association in 1855.* 
For hitherto the order of the geological succession, even as seen in the 
Geological Map of England and Wales or Ireland, as approved by Sir Henry 
de la Beche and his able coadjutors, Phillips, Ramsay, Jukes, and others, 
admits no older sediment than the Cambrian of North Wales, whether in its 
slaty condition in Merioneth and Caernarvon, or in its more altered condition 
in Auglesea. 
The researches in the Highlands have, however, shown that in our own 
islands, the older palaeozoic rocks, properly so called, or those in which the 
first traces of life have been discovered, do repose, as in the broad regions of 
the Laurentian Alountains of Canada, upon a grand stratified crystalline foun- 
dation, in which both limestones and iron ores occur subordinate to gneiss. In 
Scotland, therefore, these earliest gneissic accumulations are now to be marked 
on our maps by the Greek letter aljpha, as preceding the Roman a, which had 
been previously applied to the lowest known deposits of England, Wales, and 
Ireland. Though we must not dogmatise and affirm that these fundamental 
deposits were in their pristine state absolutely unfurnished with any living 
things (for Logan and Sterry Hunt, in Canada, have suggested that there they 
indicate traces of the former life), we may conclude, that in the highly meta- 
morphosed condition in which they are now presented to us in North-Western 
Britain, and associated as they are with much granitic and hornblendic matter, 
they are for all purposes of the practical geologist " azoic rocks." The Cam- 
brian rocks, or second stage in the ascending order as seen reposing on the 
fundamental gneiss of the North-West of Scotland, are purple and red sand- 
stones and conglomerates forming lofty mountains. These resemble to a great 
extent portions of the rocks of the same age which are so well known in the 
Longmyud range of Shropshire, and at Harlech in North Wales, and Bray 
Head in Ireland. 
At Bray Head they have afforded the Oldhamia, possibly an Alga, whilst at 
the Lougmynd, in Shropshire, they have yielded to the researches of Mr. Salter 
some worm -tracks and the trace of an obscure crustacean. 
The Highland rocks of this age, as well as their equivalents, the Huronian 
* See Reports of British Association for 1855 (Glasgow Meeting). At that time 
I was not aware that the same order was developed on a grand scale in Canada, nor 
do I now know when that order was there first observed by Sir W. Logan. I then 
(1855) simply put forward the facts as exhibited on the north-west coast of Scot- 
land ; viz., the existence of what I termed a lower or *' fundamental gneiss," lying 
far beneath other gneissose and crystaUine strata, containing remains which I even 
then suggested were of Lower Silurian age. Subsequently, in 1859, when accom- 
panied by Professor Ramsay, I adopted at his suggestion, the word "Laurentian,'* 
in comp 'tnent to ray friend, Sir VVilliam Logan, who had then worked out the 
order, and mapped it on a stupendous scale. I stated, however, at the same time, 
that, if a liiitish synonym was to have been taken, I should have proposed the word 
*' Lewisian," from the large island of the Lewis, almost wholly composed of this 
gneiss. 
