184 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 31, 



namely, from Stampekjsern, Jaegersborg, and Pusaasen, near Christian- 

 sand, from Boedalen, in Gulbrandsdalen, and dolomite from several 

 localities near Krageroe, as well as crystalline calc-spar veins near 

 Arendal ; but in none of these specimens have I found this the case ; and 

 no silica was present except that contained in the mechanically inter- 

 mixed minerals. In fact, the limestone, on the contrary, seems gene- 

 rally purer than that found in fossiliferous strata ; and this is ac- 

 counted for by the tendency which the chemical action producing 

 foliation has to separate and recombine all extraneous matters. 



In one of these limestones and in several of the azoic rocks, I have 

 found considerable per-centages of carbon present. This has also 

 been found to be the case by Kjerulf, who has found as much as 

 4^ per cent, of carbon in some of the clay-slates of Norway. 



I have also observed the frequent occurrence of graphite (which 

 may be looked upon as foliated carbon) in these rocks, often developed 

 on the sides of the joints, as in Svadsum, Gusdal, Opdal, and other 

 places. 



Again, anthracite occurs in the gneiss, at Kongsberg, and near 

 Arendal ; at the point of junction with the gneiss at Narestoe I have 

 found it in nodules in the granite. Phosphate of lime is also fre- 

 quently present in the gneiss. 



From these facts it would appear not unreasonable to question 

 whether many of the metamorphic rocks of Norway may not ori- 

 ginally have resulted from the alteration of fossiliferous strata, without 

 at the same time at all deviating from Sir Roderick Murchison's views 

 in his admirable exposition of the Norwegian Silurian system ; as we 

 may suppose that this very system may have covered considerable 

 areas of the country, and by its destruction given rise to at least some 

 part of the present metamorphic or crystalhne rocks. In fact. Sir 

 Roderick Murchison has described in his paper* a case where a por- 

 tion of the Silurian system near Christiania has actually undergone 

 a change into gneiss by contact with granite. 



Without going further into detail as to the chemical relations of 

 this part of the subject, I think that the observations and remarks 

 which I have just laid before the Society would tend to strengthen 

 the evidence in favour of the following views : — 



1 . That foliation and cleavage are two distinct processes not neces- 

 sarily connected ; and that those cases where they are parallel or 

 identical generally result from previously induced cleavage-structure. 



2. That foliated structure is the result of chemical action com- 

 bined with a simultaneous arranging molecular force, developed at 

 heats below the fusion or semi-fusion of the rock-masses ; and that, 

 when we find a similar structure induced in rocks which are known 

 to have been previously in a fused state, this has been developed 

 subsequently to the solidification of such rocks. 



3. That the arrangement of foliation is often due to the presence or 

 proximity of igneous rocks, and has a tendency to follow the direction 



* Quart. Journ. Geol. Soc. vol. i. 



