TRANSACTIONg OP THE SECTIONS. 9/ 



For hitherto the order of the geological succession, even as seen in the Geologi- 

 cal 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 sedi- 

 ment than the Cambrian of North Wales, whether in its slaty condition in Merio- 

 neth and Caernarvon, or in its more altered condition in Anglesea. 



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 Moun- 

 tains of Canada, upon a gi-and stratified crystalline foimdation, in which both lime- 

 stones and iron-ores occur subordinate to gneiss. In Scotland, therefore, these 

 earliest gneissic accumulations are now to be marked on oiu* maps by the Greek 

 letter alpha, as preceding the Roman a, which had been previously applied to the 

 lowest known deposits of England, Wales, and Ireland. Though we must not dog- 

 matise and afiirm that these fimdamental deposits were in their pristine state abso- 

 lutely unfurnished vnth. any living things (for Logan and Sterry Hunt, in Canada, 

 have suggested that there they indicate traces of the fonner life), we may conclude, 

 that in the highly metamorphosed condition in which they are now presented to us 

 in North-western Britain, and associated as they are with much granitic and hom- 

 blendic matter, they are, for all pm-poses of the practical geologist, " azoic rocks." 

 The Cambrian 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 sandstones 

 and conglomerates forming lofty moimtains. These resemble to a great extent 

 portions of the rocks of the same age which are so well known in the Longmynd 

 range of Shropshire, and at Harlech in North Wales, and Bray Head in Ireland. 



At Bray Head they have afforded the Oldhmnia, possibly an Alga, whilst at the 

 Longmynd, 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 rocks 

 of North America, have as yet afforded no trace whatever of former life. And yet 

 such Cambrian rocks are in parts of the Longmynd, and specially in the lofty moun- 

 tains of the north-western Highlands, much less metamorphosed than many of the 

 crystalline rocks which lie upon them. Rising in the scale of successive deposits, 

 we find a corresponding rise in the signs of former life on reaching that stage in 

 the earlier slaty and schistose rocks in which animal remains begin clearly to show 

 themselves. Thus, the Primordial Zone of M. Barrande is, according to that eminent 

 man, the oldest fauna of the Silurian Basin in Bohemia*. 



In the classification adopted by Sir Henry De la Beche and his associates, the 

 Lingida Flags (the equivalent of the Zone Primordiale of Barrande) are similarly 

 placed at the base of the Sihuian system. This Primordial Zone is also classed as the 

 Lowest Silurian by De Vemeuil, in Spain ; by James Hall, Dale Owen and others, in 

 the United States; and by SirW. Logan, Sterry Hunt, and Billings, in Canada f. 



In the last year, M. Barrande has most ably compared the North Ajnerican Taco- 



tion, the word ' Laurentian,' in compliment to my friend Sir WiUiam Logan, who had 

 then worked out the order in Canada, and mapped it on a stupendous scale. I stated, 

 however, at the same time, that if a British 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. 



* I learn, however, that in Bohemia Dr. Fritsch has recently discovered stratalying beneath 

 the mass of the Primordial Zone of Barrande, and in rocks hitherto considered azoic the 

 fossil burrows of annelide animals similar to those of our own Longmynd. 



t In completing at his own cost a geological survey of Spain, in which he has been occu- 

 pied for several years, and in the carrying out of which he has determined the width of the 

 sedimentary rocks of the Peninsula (including the Primordial SUurian Zone, discovered by 

 that zealous explorer, M. Casiano de Prado), M. de Vemeuil has in the last few months 

 chiefly examined the eastern part of the kingdom where few of the older palaeozoic rocks 

 exist. I am, however, informed by him, that Upper Silurian rocks with Cardiola interrupta, 

 identical with those of France and Bohemia, occur along the southern flanks of the Pyre- 

 nees, and also re-occur in the Sierra Morena, in strata that overhe the great mass of Lower 

 Silurian rocks as formerly described by M. Casiano de Prado and himself. The southern 

 face of the Pyrenees, he further informs me, is specially marked by the display of miu-al 

 masses of Carboniferous strata, which, succeeding the Devonian rocks, are not arranged in 

 basin-shape, but stand out in vertical or highly inclined positions, and are followed by 



1861. 7 



