80 RBPORT-^1855. 



On the Relations of the Silurian and Metamorphic Rochs of the South of 

 Norway. By David Forbes, F.G.S. 



A number of large sections were exhibited, showing the relative positions of these 

 rocks, and their structure dwelt upon at length. It was shown, by overlook- 

 ing the foliation of the metamorphic rocks, and by keeping in view the mineral 

 character of the rock masses themselves, that the crystalline rocks of Norway, 

 hitherto considered as irresolvable, would be found conformable to the Silurian 

 formation above them, and that they could be regarded as altered sedimentary rocks, 

 probably analogous to the Cambrian sandstones and shales of Wales. 



Some of the hornblende gneiss was even shown to be above the Devonian sand- 

 stones, and to correspond to argillaceous shales of other parts of Norway. 



It was contended that the felspathic and massive gneiss of the South of Norway 

 was in great part, if not altogether, granite, with a superinduced foliated structure ; 

 and the large sections and plans showed full evidence of its having been eruptive. 



Remarks on the Cleavage of the Devonians of the South of Ireland. 

 By Professors Harkness and Blyth. 



The counties of Cork and Kerry present several features of an interesting nature, 

 as far as regards cleavage. Beds affording this structure are intimately associated, 

 and interstratified with others which are devoid of cleavage ; and from several 

 analyses it would appear that the cleaved strata possess a greater amount of 

 alumina than such deposits as want this structure. The specific gravity of the 

 cleaved strata is also greater than where this mode of arrangement does not occur. 



The angle of the cleavage planes varies with the chemical composition of the rock 

 in which this structure appears; the greater the proportional amount of alumina, the 

 greater is the angle of cleavage. 



In the county of Cork the strike of the cleavage planes accords with the strike of 

 the rolls, which the Devonian strata have in this district been subjected to, and is 

 in an east and west direction. In the county of Kerry the same circumstance 

 obtains, but here the strike of the roll is not so regular as in the former county. 

 In the island of Valentia the intimate connexion which exists between the opera- 

 tions of the force producing rolls and that from whence cleavage originates is well 

 seen. Here the strikes are E. and W., E.N.E. and W.S.W., and N.N.E. and 

 S.S.W., and with these several strikes the planes of cleavage agree. The cleavage 

 is also most perfect in those localities where the rolls are best developed, and all the 

 features presented by the cleavage of the Devonians of the south of Ireland support 

 the inference that this structure owes its origin to that force which has subjected 

 the deposits to a series of rolls ; and that those beds exhibit this structure best 

 which were originally of a soft shaly nature, being composed of particles capable 

 of rearranging themselves at right angles to the planes of pressure. 



On the Lowest Sedimentary Rocks of Scotland. 

 By Professor Harkness, F.G-S. 

 The axis of the lower Silurians of the south of Scotland traverses the counties of 

 Roxburgh and Dumfries, and in connexion with this axis are found the lowest 

 sedimentary rocks of Scotland. The nature of the strata composing the axis is 

 arenaceous ; and beds of this character are well seen in the course of the Dryffe 

 water in the latter county. These beds are overlaid both on their north and south 

 side by thin bedded greywacke sandstones and shales which are much flexured, and 

 in one locality afford slaty beds, which seem to be the result of the flexures to which 

 the strata have been subjected. At Brinks in Roxburghshire the thin greywacke 

 shales aflFord evidence of the existence of animal life in the form of tracks of animals 

 traversing mud, and these tracks bear the appearance of having resulted from crus- 

 taceans. They are the earliest traces of animal life which have yet been detected in 

 Scotland. The same beds also are marked by desiccation cracks, furnishing the 

 earliest direct proofs of the existence of dry land. They are likewise gently rippled, 

 and seem to have originated from littoral conditions. Some higher beds contain 

 Protovirgularia, and above these are found the graptolite shales, which have previ- 



