1884.] on the Building of the Alps. &5 



their beds of quartzite and of limestone, we may mark the gradual 

 approach to a more normal condition of things. Some, such as the 

 Lustrous Schists, may indeed be contemporaneous with our earliest 

 Palaeozoic rocks ; but I confess that to myself the evidence appears 

 more favourable to the idea that all are more ancient than the period 

 which we call Cambrian, and that the majority are so I feel little 

 doubt. 



Supposing, then, that I am right in considering all the Aljjine 

 schists, even the Lustrous group, to be pre- Cambrian, we have a vast 

 interval of time which has left no record in those districts of the 

 Alps of which I have been speaking. It is not till we come to the 

 Carboniferous period that we can identify any pages in the life history 

 of the earth. We are justified with regard to these in the following 

 conclusions : — 



That in the place of the Alps there was at that time an up- 

 land district, composed of gneisses and schists, in substantially the 

 same mineral condition as they are at present, together with slaty 

 beds in a comparatively unaltered condition, which district was 

 fringed by a lowland covered by a luxuriant vegetation. Prior to 

 this time, also, the metamorphic rocks of the Alps had been so far 

 folded and denuded that the coarser gneisses were in many places 

 laid bare, and contributed the materials which we now find in such 

 beds as the Val Orsine Pudding stone. Whether there was a pre- 

 Triassic mountain chain occupying some part of the present Alpine 

 region we cannot venture to say, but I think we may unhesitatingly 

 affirm that there were pre-Triassic highlands. 



After the close of the Carboniferous period, and anterior to the 

 middle part of the Trias, there were volcanic outbursts on a large scale 

 in more than one region of the Alps — notably in the district near and 

 to the east of Botzen. After this commenced a period of subsidence 

 and of continuous deposition of sediment. This seems to have begun 

 earlier and to have been at first more rapid in the eastern than in the 

 western area. Since in the former the Triassic beds are generally much 

 thicker and more calcareous than in the latter, one is tempted to 

 imagine that the eastern area quickly became a coraliferous sea, with 

 an occasional atoll or volcanic island. Henceforward to the later part 

 of the Eocene the record is generally one of subsidence and of deposit 

 of sediment. Pebble beds are rare : the strata are grits, shales (or 

 slates), and limestones. Whence the inorganic constituents of these 

 were derived I cannot at present venture to suggest, but though con- 

 glomerates are rare, there are occasional indications that land was not 

 very distant. In the eastern Alps, however, the position of some of 

 the Cretaceous deposits and the marked mineral differences between 

 these and the Jurassic seem to indicate disturbances during some 

 part of the Neocomian, but I am not aware of any marked trace of 

 these over the central and western areas. The mountain-making of 

 the existing Alps dates from the later part of the Eocene. Beds of 

 about the age of our Bracklesham series now cap such summits as 

 Vol. XL (No. 78.) f 



