126 Notices of Memoirs—Prof. M. Bertrand— 
to the secondary influence of the neighbouring masses. Taken thus, 
this formula only differs from that by which I attempted before to 
summarize the Alpine movements in that, as regards the latter, the 
successive slices are precisely the beds themselves, the planes of 
division being the planes of stratification, and therefore almost 
indefinite in number. In Scotland, as in the Alps, the pressures at 
first would form an arch, then, as they became greater, the arch in 
the one case would be bent downwards, and in the other would 
break. Pressure continuing, sliding movements would take place, 
following the bedding in the reclining fold, and following the 
fractures in the broken one. The difference between the two regions 
would be due to a difference in plasticity, i.e. to a difference of 
weight or thickness in the masses compressed. It will be seen how 
well this explanation agrees with the theory,! according to which 
the thickness of the superficial rocks compressed in consequence of 
the cooling of the earth increases with time. The differences 
between the mountains of Scotland and the Alps would be a question 
of time. No doubt this is yet but a hypothetical consequence; it 
may be added, however, that it is further confirmed by a comparison 
with the Coal-measure range. This chain, so well studied by Prof. 
Gosselet in the Ardenne, presents, on the borders of the coal-field, 
an intermediate structure, the part played by faults being there 
more accentuated than in the Alps, and less so than in Scotland. 
In any case, I cannot share Mr. Cadell’s opinion when he says that 
in examining the Alps by the light of the new facts recognized in 
the Highlands, and confirmed by laboratory experiments, the same 
structures will be found there. It is not the observers who are at 
fault, it is the mountains which are not the same. 
III. Side by side with the study of the movements themsélves 
‘must be noted that of the metamorphism due to them. Nowhere, 
perhaps, outside the works of Reusch, in Norway, have clearer or 
more instructive examples been described. In the conglomerates, 
pebbles are seen to lengthen in the direction of the movement, 
sericite is developed in the quartzites, transforming them into 
micaceous schists traversed by little felspathic veins (“veins of 
pegmatite’’). All these effects go on increasing as one approaches 
the east, and beneath the last great thrust plane we were enabled to 
see a remarkable section where, by reason of the repetition of the 
beds, one can follow almost step by step the progress of trans- 
formation, to a point at which the beds altogether cease to be 
recognizable, and can no longer be distinguished from the mass of 
crystalline schists (‘‘ Moine Schists”?) which surmount them. 
At other points, on the contrary, where the upper “story” (in 
consequence of a lesser degree of denudation) advances further to 
the west, the separation of the two systems is clear and distinct; 
there is then found at the base of the crystalline schists a veritable 
that the Scottish sections exhibited the material realization of this theoretical idea. 
Comptes Rendus Acad. Sci. 29th December, 1890, Report of M. Daubrée on the 
“ Vaillant’’ prize. 
1 Davison and Darwin, Phil. Trans. Roy. Soc. 1887, p. 281. 
