508 Prof. Bonney—Crystalline Schists of the Alpine Chain. 
having carefully studied not a few of the sections on which it rests, 
that they prove either nothing or the contrary. 
Time will be saved in discussing these sections by making two 
statements: First that I have never succeeded in finding a shale of . 
later Paleozoic or Mesozoic age converted by dynamometamorphic 
action into anything more than a phyllite—meaning thereby a slaty 
rock, which retains many traces of a sedimentary origin and in which 
the authigenous mica, though very abundant, can only be distinguished 
on microscopic examination, while that mineral in the ordinary 
crystalline schists of the Alps is much larger and is easily seen with 
the unaided eye. But a minute mica, like that of a phyllite though 
generally a little larger, may appear when a schist, gneiss, or granite 
has been crushed, and, besides this, the original mica may be reduced 
to small fragments. In such case the two schistose rocks may seem 
to be identical, but the difficulty of distinguishing them is restricted 
to a very narrow zone." 
The other point is that in a region much affected by folding and 
thrust-faulting the apparent succession of a series of rocks is not only 
without chronological value but may be actually misleading. It has 
had this effect on the authorities in whom Dr. Preller trusts,as I will 
endeavour to show as briefly as possible. His first paper describes 
the ‘‘ Permian formation in the Alps of Piémont, Dauphiné, and 
Savoy ’’, and I happen to be acquainted with some of the sections 
there cited, as, for instance, those between Bourg d’Oisans and- 
Briancon and those to the south of the Mont Blanc range. In regard 
to the former I cannot venture to say how much of the great zone of 
non-crystalline rocks between Argentiére and Moutiers is Permian 
(the Carte Géologique de la France makes the whole Upper 
Carboniferous, with a little overlying Lower Trias), but the two 
sharp infolds of the former on either side of Freney on the western 
side of the Lautaret pass are perfectly distinct from the enclosing 
gneiss, and ordinary Liassic strata. rest upon both it and their 
denuded edges; overlying the former to beyond the Col du Lautaret, 
at elevations ranging from about 5,000 feet to 11,000 feet above the 
sea. Over this considerable area Permian and Trias are either absent 
or inconspicuous, at any rate till we come towards Briangon. As, 
however, I maintain that none of the stratified rock in this zone, 
whether later Paleozoic or earlier Mesozoic (which I have also 
examined in two or three places further north), is more metamorphosed 
than many grits and slates in Britain of the same geologic age, and 
that the Jurassic limestones do not differ appreciably from those in 
other parts of the Alps, I regard the exact geological position of the 
aforesaid deposits as unimportant. This, at least, is certain, that the 
Alpine rocks were affected by great earth-movements in both pre- 
Carboniferous and pre-Triassic times, and that the latter system was 
deposited on a very irregular surface, for in some places it is missing, 
in others it appears as that peculiar calcareous material called 
rauchwacké (often with gypsum), and in others as a group of ordinary 
stratified rocks, often limestones or dolomites. : 
1 Q.J.G.S., 1884, pp. 4, 5, 21; 1889, p. 92, and remarks on rocks of the 
pietre verdi type at p. 98. 
