198 PROF. T. G. BOJ^IfEY ON CRYSTALLINE SCHISTS AND THEIR 



and the calc-mica schists seems to he too abrupt to be explicable by 

 the difference in their chemical composition. In addition to these 

 difficulties there is a further one, which to myself seems also of 

 great weight. In the Alps crystalline limestones and calc-mica 

 schists are anything but rare. These rocks differ in no respect of 

 the slightest importance from those at Altkirch, and they are asso- 

 ciated again and again, under circumstrnces which preclude the 

 possibility of error, with other true crystalline schists (micaceous, 

 chloritic, &c.). Such rocks, wide as is my experience, I have never 

 seen in nndoubted sequence or intercalation with true phyilites, nor 

 have I found, even in the most highly disturbed regions occupied by 

 Mesozoic strata, crystalline limestones and calc-mica schists (not 

 even in the most restricted areas) which presented any real resem- 

 blance to those which abound in the other (and, as I believe, much 

 older) series. Yet probably few geologists have had better oppor- 

 tunities of meeting with such rocks if they really did occur in the 

 Alps. Surely, then, if the " upper schists " (as I have termed them) 

 are merely Jurassic sediments, to which a crystalline structure has 

 been given in the process of mountain-making, these cases of transi- 

 tion, these instances of resemblance, should be of common occur- 

 rence. There should he a frequent tendency among the sediment- 

 aries to assume the crystalline character, among the crystallines to 

 revert to the sedimentary. This argument will perhaps not appeal 

 very strongly to those who have devoted themselves to a minute and 

 elaborate mapping of a single district ; but I am confident of its 

 effects with those who have compared rock with rock, and section 

 with section, from one end of the Alps to the other. 



Thus the Altkirch section, a difficult and perplexing one in any 

 case, presents us with such anomalies, if interpreted as a case of 

 selective metamorphism in a group of Jurassic rocks, that it must 

 not be made the basis of a theory which is to be applied with un- 

 questioning confidence to every part of the Alps. As it seems to 

 me, the evidence tendered on the spot demands a verdict of " not 

 proven ; " that obtainable in other parts of the Alps, as I now hope 

 to show, will compel us to add ••' not provable ■' *. 



* I ought to mention that Stapf, in bis description of the rocks from the St. 

 Gothard Tunnel, states that he finds in one rock (No. 43), about 2600 metres 

 from the north entrance, organic remains like sponges, corals, or Polyzoa. One 

 of these he figures and describes (Zeitschr. d. deutsch. geol. Gesellsch, xxx, 

 p. 130, pi. vi.). He admits that in the same rock a network structure occurs 

 which is due to the infiltration of graphite into the cleavage-planes of calcite. 

 I have examined microscopically specimen No. 43 in the collectio}i belonging to 

 the British Museum, and cannot satisfy myself that there are any true remains 

 of organisms, but think that the imitation structures (often very curious) are of 

 mineral origin. A remarkable pseudo-organic structure is described by Px'of. 

 Heddle (Min. Mag. vol. v. p. 27^), and the same epithet, as is well known, 

 would be applied by many to Eozoon. The rock itself macroscopically and 

 microscopically appears to me to be closelj^ related to the crystalline limestone 

 described above, and to differ much from any Mesozoic limestone known to me. 

 After arriving at this conclusion, I found that Dr. Otto Meyer and Prof 

 Zirkel were of the same opinion (Untersuchungen iiber die Gesteine des Gothard- 

 tunnels ' (Inaug. Diss.), Leipzig, 1870). For the above references I ain indebted 

 to Mr, Miers. The rock which has furnished No. 43 lies just south of the schis- 

 tose slate described above, and appears to pass into the white fissile marble. 



