XIV.] THE GEOLOGY OF THE ALPS. 335 



tire distance of the tunnel, which, it will be remembered, passes 

 from near Modane in Savoy to Bardonecchia in Piedmont 

 (about fifteen miles to the southwest of Mont Cenis), a distance 

 of 12,220 metres. The direction of the tunnel is N. 14 "W., 

 and the dip of the strata throughout nearly uniform, N. 55 W., 

 at an angle of about 50. From this we deduce by calculation 

 that the vertical thickness of the strata is equal to nearly 60 

 per cent of the distance traversed, or in round numbers about 

 7,000 metres. Of this not less than 5,831 metres, beginning at 

 the southern extremity, are occupied by lustrous and more or 

 less talcose schists with crystalline micaceous limestones, often 

 cut by veins of quartz with chlorite and calcite. Above there 

 are 515 metres in thickness of alternations of anhydrous sul- 

 phate of lime (karstenite) with talcose schist and crystalline 

 limestone. The anhydrite enclosed lamellar talc in irregular 

 nodules, with dolomite, crystallized quartz, sulphur, and masses 

 of rock-salt. This was overlaid by 220 metres of quartzite, 

 occasionally alternating with greenish talcose schists, and en- 

 closing veins and masses of anhydrite. A considerable break 

 occurs in the series of specimens above this, but for the distance 

 of 1,707 metres from the northern entrance to the tunnel, 

 corresponding to a vertical thickness of 1,024 metres, we have 

 principally sandstones, conglomerates, and argillites, occasionally 

 with anthracite. The serpentines and euphotides which ap- 

 pear among the crystalline schists at Bramant, near the line of 

 the tunnel, were not met with, nor was the underlying gneiss 

 encountered. The work terminated at Bardonecchia among the 

 crystalline limestones. 



According to Sismonda and Elie de Beaumont, there is 

 throughout this entire section no evidence of inversion, dislo- 

 cation, or repetition in the series of 7,000 metres of strata, a 

 conclusion which they support by very cogent arguments. 

 Lory, on the contrary, while he agrees with the observers just 

 mentioned in looking upon the crystalline strata as altered 

 mesozoic, conceives them to include both trias and lias, and to 

 be- placed beneath the true carboniferous by a great inversion 

 of the whole succession. This series of crystalline rocks is 



