236 DR. J. W. GREGORY OX THE WALDENSIAN [May 1 894, 



sediments of Gastaldi's ' pietre verdi ' group. This subject will be 

 dealt with in a subsequent communication by Mr. A. M. Da vies, of the 

 Royal College of Science, London, and myself. Mr. Davies gave me 

 the great benefit of his assistance, as well as the pleasure of his 

 company, during the examination of the gneiss. I must moreover 

 express my thanks to Prof. Sacco for the opportunity of examining 

 the rock-collections named by Sismonda at Turin ; also to Dr. G. Gia- 

 notti, who guided us over the sections described by him on the south 

 side of the Valle Grande at Chialamberto ; to Signor Tng. Sommariva, 

 to whom we are indebted for much information regarding, and the 

 opportunity of a visit to, the Vonzo mines ; and to Prof. Stevens, of 

 Turin, whose kind help added much to the pleasure of a visit to the 

 Valle Grande. 



II. The Cottian Sequence and Previous Literature thereon. 



Even before Fournet's ' Memoire sur la Geologie de la partie des 

 Alpes comprise entre le Yalais et l'Oisans ' 1 and Lory's monograph, 

 ' Description geologique du Dauphine,' 2 had given a comprehensive 

 view of the main features of the structure of the Cottians, it had 

 acquired a somewhat extensive literature, dating from the works of 

 Paujas St. Pond (1751), Pobilant (1786), Morozzo (1793), and 

 de Saussure (1796). We owe to M. Kilian 3 a bibliography of the 

 French side of the range, and to Prof. Baretti and Dr. Portis 4 a 

 similar work for the Italian ; they are brought up to 1891 and 1881 

 respectively. It is, however, here unnecessary to refer to the earlier 

 literature as, with the exception of the absolute age of some of the 

 schists and sediments, there has been a general agreement amongst 

 recent writers as to the relative age of the whole series. Lory, it 

 is true, regarded the ' schistes lustres' of Cesana as Triassic, a view 

 recently put forward again on pakeontological grounds, but he fully 

 accepted them as younger than the underlying schists and both as 

 newer than the gneiss. 



The question of the relations of the gneisses and the schists has 

 been twice discussed in recent years, and it is only necessary to refer 

 to those two memoirs. In 1887 Zaccagna published his well-known 

 paper ' Sulla Geologia delle Alpi occidentali,' 5 in which he described 

 in detail five sections across the Western Alps from Mont Blanc to 

 east of the Col di Tenda. He recognized the following sequence : — 



1 Fournet, Ann. Soc. roy. Agric. Lyon. ser. 1, vol. iv. (1841) pp. 105-183, 

 483-560 ; vol. ix. (1846) pp. 1-112; ser. 2. vol. i. (1849) pp. 185-269, pi. i. 



2 Lory, Bull. Soc. Stat. Isere, ser. 2, vol. v. (1861) pp. 1-240, pi. i. ; ser. 2, 

 vol. vi. (1861) pp. 1-260, pis. ii., iii. ; ser. 2, vol. vii. (1864) pp. 4-252, map. 



3 Kilian, " Notes bibliographiques pour servir a l'histoire geologique des 

 Alpes franchises— Le Dauphine," nos. 1500-1566, An 26-27, 1890-91. 



4 ' Bibliographic g6ologique et paleontologique de l'ltalie,' 2& me Oongres 

 Geol. Internat. Bologna, 1881, pp. 3-36. 



5 Zaccagna, Boll. E. Com. geol. Italia, vol. xviii. (1887) pp. 346-417, 

 pis. ix.-xi. 



