ANNIVERSARY ADDRESS OF THE PRESIDENT. cxlix 



states his belief that the limestones intercalated with the chloritic 

 and quartzose rocks of Dumbartonshire are unquestionably of Lower 

 Silurian age, and that the overlying masses of mica-schist and 

 quartzose-gneissic flagstones of the Breadalbane district may be some 

 day found to be merely the prolongation of the micaceous flagstones 

 of the North- Western Highlands, described as overlying the quartz- 

 rocks and fossiliferous limestones. 



The inquiry was then extended, ably and extensively, into the 

 Devonian system ; and, after many judicious observations on the divi- 

 sions and arrangement of this great formation, Sir Roderick main- 

 tains the importance of the Devonian series in the scale of formations, 

 and that the Old Red Conglomerates, ichthyolitic schists, and corn- 

 stones, with the overlying sandstones of Scotland and Herefordshire, 

 fully represent, in time, the Devonian rocks of the South of England 

 and the Continent, so full of corals, crinoids, and marine mollusks. 



It is impossible, in noticing this paper, not to dwell for a moment 

 on two interesting points connected with it ; namely, that the recog- 

 nition of the Silurian age of the Durness deposit should have been 

 made, not through the intervention of a comparison of its fossils with 

 those of the closely approximate Silurian regions of England, but 

 with the remote Silurian regions of America, and it may be said that 

 the Silurian deposits of Ireland are perhaps richer in American fossils 

 than the English deposits. Supposing these relations true, many 

 curious speculations might be founded upon them worthy of the 

 attention of Mr. Austen. The next is the superposition of completely 

 metamorphosed rocks over others in a comparatively slightly modified 

 condition, passing as it were in a diminishing degree of metamor- 

 phism, from the supposed younger gneiss above, through micaceous 

 flags, to the semicrystalline limestone with fossils. This seems to 

 be a matter full of interest, and, assuming that the geological facts 

 are correct, implies that we have yet much to learn respecting 

 the true nature of metamorphism, at least as to the mode in which 

 metamorphic action has been exercised; but I must still refrain 

 from giving a decided opinion on a subject so replete with difficulties, 

 in which two such able observers as Sir Roderick Murchison and 

 Professor Meol are still at issue. 



The papers I have hitherto noticed have been prepared in con- 

 formity with the ordinary rules of the Society, and have more or 

 less contributed to our knowledge in some one or other of the lead- 

 ing branches of geological science. The papers I am now about to 

 refer to are, in some respects, less conformable to the rules of the 

 Society, but are by no means devoid of interest and value, as 

 they are intended to facilitate the appreciation of the labours of our 

 Transatlantic brethren, by submitting them to us in a well-arranged 

 and carefully considered form. Ton are all aware that Dr. Bigsby, 

 the author of these papers, has never lost the enthusiasm which his 

 travels, on a public and important duty, through the most remote 

 and wild regions of North-west America, excited in his mind nearly 

 forty years ago. I well remember him at that time, when his 

 energies were at their maximum; and the bent of his mind was 



vol. xrv. I 



