Intelligence and Miscellaneous Articles. 547 



2. ' The " Schistes Lustres " of Mont Jovet (Savoy).' By J. W. 

 Gregory, D.Sc, F.G.S. 



The author gives a history of the controversy as to the age of the 

 ' schistes lustres ' of the Western Alps, making special reference to 

 the views of Zaccagna and Bertrand concerning the schists of Mont 

 Jovet. Of these writers, the former maintains that the rocks of the 

 summit of the mountain are old rocks on which the Carboniferous 

 and Triassic strata were deposited unconformably ; while, according 

 to the latter author, the rocks forming the top of the mountain were 

 laid down after those which flank it. 



In the present paper the author gives the results of an examina- 

 tion of the rocks of Mont Jovet recently made by him. He contends 

 that Lory and Zaccagna were correct in identifying the central rocks 

 of Mont Jovet as e schistes lustres,' for this conclusion is supported 

 by their lithological characters and the occurrence of basic igneous 

 rocks of the ' pietre-verdi ' type associated with them, and is not 

 opposed to their stratigraphical relations. It is further maintained, 

 as the result of the evidence collected by the author, that the schists 

 in question are older than the Trias ; for fragments of the schists 

 occur in the Trias, there is a discordance of strike between the two 

 series, masses of dolomite rest unconformably upon the flanks of the 

 schists, and the Trias has escaped metamorphism which the schists 

 have undergone. The probabilities are in favour of the schists 

 occupying the same relation to the Carboniferous as they do to the 

 Trias ; while the close approximation of the schists to the former 

 shows that the schists are not the altered representatives of the 

 neighbouring Carboniferous beds, and it is therefore concluded that 

 the ' schistes lustres ' are pre-Carboniferous, but evidence by which 

 finally to assign them to any exact horizon before this date is still 

 wanting. 



L. Intelligence and Miscellaneous Articles. 



ON THE WAVE-LENGTH OF THE D 3 HELIUM LINE. 

 BY A. DEFOREST PALMER, JR. 



/"^"WTNGr to the recent increased interest in the wave-length of 

 " the helium lines due to the discovery of terrestrial helium, I 

 have been led to calculate some observations on the D 3 chromo- 

 sphere line carried out by myself at the Physical Laboratory of the 

 Johns Hopkins University during February and March 1893. 



The measurements were made on the large fixed telescope- 

 spectrometer, used by Dr. Louis Bell* in his determination of the 

 absolute wave-length of the D solar lines, with a plane speculum 

 metal grating having about fourteen thousand lines to the inch and 

 5 inches of grating-space. The telescopes of this instrument 

 are 16*4 centim. clear aperture and about 2*5 metres focal length ; 

 and with the grating used I obtained good dispersion and excellent 

 definition in the first spectrum to the right of the normal to the 



* Amer. Journ. Sci. vol. xxxv. p. 265 ; Phil. Mag. 1888, xxv. p. 245. 



