1848.] MURCHISON ON THE STRUCTURE OF THE ALPS. 2:U 



tortoises and the great aquatic salamanders of the lakes, as well as 

 the marine shells of the then bays of the sea, are all unanswerable 

 evidences of a very different climate from that which now prevails. So 

 far we can without difficulty picture to ourselves the former state of 

 things during the accumulation of the molasse. But when we attempt 

 satisfactorily to analyse the physical changes even of this sera, we 

 encounter considerable difficulties. The boldest speculator may be 

 well startled when he is called upon to explain the modus operandi 

 by w'hich regularly stratified masses, thousands of feet thick and for 

 the most part formed under fresh water, have been piled up one on 

 the other. He may at first suppose that the well-rounded Alpine 

 pebbles in these strata resulted from the action of various rivers ; 

 but a survey of the region soon convinces him that such local causes 

 would be wholly inadequate to explain such a general phsenomenon. 

 The grandeur, width, depth, and, above all, the longitudinal persist- 

 ence of this enormous mound of detrital, yet finely laminated mate- 

 rials, ranging as it does along the whole external northern face of the 

 chain, can never be explained by the action of separate rivers which 

 issued from openings into insular lands, unquestionably of much less 

 height than the present Alps. Such lands could only give rise to small 

 partial deltas, each streaming out from the centre of their origin like 

 spokes in a wheel, and could never have produced the one gigantic ac- 

 cumulation of the molasse and nagelflue, which does not run far up 

 into the recesses of the Alps, but constitutes, on the contrary, their 

 broad, external barrier. It may, indeed, be suggested that the detritus 

 resulting from innumerable small torrents descending from a precipi- 

 tous rocky isle, were accumulated on a steep shelving shore, like that 

 of the present Maritime Alps ; but however this may have been, it is 

 manifest that the bottom of the waters which bathed that shore, 

 whether freshwater, brackish or marine, must have been successively 

 depressed to enormous depths. This long-continued depression can 

 indeed alone enable us to account for the heaping-up of these sub- 

 aqueous materials throughout such a thickness, and consequently 

 during so long a period. It is also self-evident, that whilst they were 

 depositing, the materials of the molasse must have been arranged in 

 strata which sloped away from their parent rocks of the Alps. 



At this point, then, in the history of these mountains, we can arrive 

 by an interpretation of the materials in our hands. But with the 

 close of the molasse period, a change came over the surface, compared 

 with which all antecedent pheenomena fade away in importance. 

 The very deposits of molasse and pebbles, which till then formed 

 sloping deposits on the shore, or more or less grand horizontal 

 masses at certain distances from it, suddenly underwent those 

 powerful upheavals parallel to the lines of dislocation of the adjacent 

 chain ; — movements which not only threw up horizontal strata into 

 vertical axes, but cast down the youngest accumulations of that long 

 period into positions which make them appear to pass under the very 

 rocks out of which they had been formed. Although in estimating 

 such gigantic movements the powers of imagination are at fault, 

 surely it is not unphilosophical, with such unanswerable data before 



