2 DE. J. W. GBEG0KY ON THE ; SCHISTES [Feb. 1 896, 



west of Mont Jovet. In consequence of this, Fournet, 1 in his map, 

 marked the whole of the rocks of the mountain as Jurassic ; while, 

 later on, Lory, 2 who knew the locality well, identified the schists 

 and limestones of the summits as altered Trias. In spite of the 

 protests of the Italian geologists, who referred the ' Schistes lustres 7 

 either to the early Palaeozoic 3 or to the Archtean crystalline series, 4 

 the weight of Lory's influence gained general acceptance for his 

 view. It was not till 1887 and 1889 that Zaccagna 5 and Bonney 6 

 carried the controversy into the third phase by the independent 

 description of some sections across the Cottian Alps, which showed 

 a marked unconformity between the Trias and the ' schistes lustres/ 

 and thus proved the pre-Mesozoic age of the latter. 



These two papers both described areas which Lory had previously 

 mapped, and on which he rested his conclusions. In spite, there- 

 fore, of the clearness of the descriptions of the two authors, their 

 conclusions have not been generally accepted. The official map of 

 the French Geological Survey on the scale of 1 : 1000,000, issued 

 in 1889, is coloured in accordance with Lory's views. Diener, 7 

 though accepting most of the ' Kalkschiefer ' (or ' schistes lustres ') 

 as pre-Mesozoic, still includes part of them in the Trias. Kilian, 8 

 in his lucid and judicious discussion of the question, holds that as 

 the presence of these schists seems to exclude that of the Carboni- 

 ferous, it is possible that they are the altered representatives of the 

 rocks of this system. Parona's 9 discovery of radiolaria in the 

 schists in the typical sections near Cesana has thrown further doubt 

 on the Archaean age of the beds ; while, still more recently, Marcel 

 Bertrand 10 has gone back unreservedly to the theory of the Mesozoic 

 age of the ' schistes lustres.' 



1 J. Fournet, ' Memoire sur la Geologie de la partie des Alpes comprise 

 entre le Valais et l'Oisans,' Ann. Soc. roy. Agric. Lyon, ser. 2, vol. i. (1849) 

 pp. 201-202, pi. i. 



2 C. Lory, ' Description geologique du Daupbine,' Bull. Soc. Stat. Isere, 

 ser. 2, vol. vii. (1864) p. 16 ; ' Carte geologique de la Maurienne et de la 

 Tarantaise (Savoie),' Bull. Soc. geol. France, ser. 2, vol. xxiii. (1866) p. 481 ; 

 ' Sur la Constitution et la Structure des Massifs de Schistes cristallins des Alpes 

 occidentales,' Compt. Bend. Congres Geol. Internat. sess. 4 (Londres, 1888), p. 93. 



3 As, e. g.. B. Gastaldi, ' Studii geologici sulle Alpi occidentali,' pt. i., Mem. 

 descriz. Carta geol. Italia, vol. i. (1871) pp. 16-19. 



4 As, e. g., M. Baretti, ' Studi geologici sulle Alpi Graie settentrionali,' 

 Mem. E. Accad. Line. ser. 3, \ol. iii. (1879) pp. 484-486, pi. i. 



5 D. Zaccagna, ' Sulla Geologia delle Alpi occidentali,' Boll. E. Com. geol. 

 Ital. vol. xviii. (1887) pp. 346-417, pis. ix.-xi. 



6 T. G. Bonney, ' Notes on Two Traverses of the Crystalline Eocks of the 

 Alps,' Quart. Journ. Geol. Soc. vol. xlv. (1889) pp. 67-109. 



7 Diener, ' Gebirgsbau der Westalpen', Vienna, 1891, p. 103. 



8 W. Kilian, ' Notes sur l'Histoire et la Structure geologique des Chaines 

 alpines de la Maurienne, du Brian <;-onnais et des Begions adjacentes,' Bull. 

 Soc. geol. France, ser. 3, vol. xix. (1891) pp. 579-580. 



9 C. F. Parona, • Sugli Schisti silicei e radiolarie di Cesana presso il Mon- 

 ginevra,' Atti E. Accad. Sci. Torino, vol. xxvii. (1891-92) pp. 305-319. 



10 Marcel Bertrand, ' Etudes dans les Alpes Franchises.— Structure en Even- 

 tail, Massifs amygdaloides et Metamorpbisme,' Bull. Soc. geol. France, ser. 3, 

 vol. xxii. (1894) pp. 69-118, pis. iv.-vi. ; 'Schistes lustres de la Zone centrale,' 

 ibid. pp. 119-162, pi. vii. 



