190 PROF. T. G. 13UXNEY OX CRYSTALLINE SCHISTS AND THEIR 



either to pulverization of the rock by pressure, or to the inclusion of 

 a later series by folding or faulting. 



But while there can be no doubt of the general truth of this 

 statement, it has recently been asserted that in certain districts of 

 the Alps there is a passage from Jurassic rocks into trulj' crystalline 

 limestones, while in others fossils of that age occur together with 

 garnet, mica, and a mineral resembling staurolite, in schists which 

 cannot be distinguished from certain members of the above-named 

 group *. If this assertion be correct, it must follow (1) that the 

 Alps exhibit true schists which are metamorphosed sediments of 

 Mesozoic age, and (2) that, inasmuch as these are undistinguishable 

 from schists which by stratigraphical evidence can be proved to be 

 very much older than any Mesozoic rock, a schist, like a granite or 

 a dolerite, might belong to almost any geological epoch. 



This last opinion can claim the sanction of antiquity and the 

 authority of weighty names, but the progress of investigation had 

 largely diminished the number of its supporters, when it seemed to 

 receive a new life from a recognition of the amazing effects of me- 

 chanical forces in modifying rock-structures and from the above- 

 named discoveries in the Alps. Specimens illustrative of the latter 

 were exhibited at the International Geological Congress in Sep- 

 tember 1888. Those supposed to indicate the passage of an ordinary 

 Jurassic limestone into a crystalline marble (from a district which I 

 had already visited) did not appear to me convincing. But those ex- 

 hibiting fossils in a rock resembling a true schist were certainly very 

 remarkable, and seemed to afford considerable support to the opinion 

 mentioned above. I was not, however, convinced by them, because 

 though I had not examined the two localities in which the supposed 

 '• fossiliferous schists" occurred, I was fairly acquainted with the 

 geology of the district, and had been very near, in one case within 

 less than a mile, to each locality. I had also examined rocks iden- 

 tical, as I believed, with those in which the fossils occurred. The 

 knowledge thus obtained, notwithstanding the apparent evidence 

 of the specimens exhibited, suggested to my mind the possibility of a 

 mistake, and a doubt whether the identity of tlie fossiliferous rock 

 with the true schists of the district was not more apparent than 

 real. Still so remarkable were the specimens, so great was the 

 weight of authority, that when these cases were quoted against me 

 in the discussion on my paper, I departed from that which has 

 become almost a rule to me — viz., to pay no regard to criticisms 

 founded on second-hand information — and stated that I accepted the 

 challenge. A part of my last summer vacation was devoted to the 

 study of the district. I had hoped to have been aided by my old friend 

 and fellow-worker Mr. Hill, but his entry upon a new field of duty 

 prevented him from leaving England. I had, however, the good 

 fortune to obtain the company of Mr. J. Eccles, F.G.S., who joins to 



* As the volume of papers presented at the Geological Congress has not yet 

 been published, it will be better to refer, not to the copies then distributed, 

 but to the translations by Dr. Hatch, printed in ' Nature,' Sept. 27 and Oct. 4, 

 1888 : see especially p. 524. 



