298 PREHISTORIC EUROPE. 



there could be no doubt, were of fluviatile origin, and they 

 indicated a time when the rivers flowed at considerably higher 

 levels than those of the present day. One of these terraces 

 borders the Ehine at Camischollas, above Disentis, at 4400 feet 

 above the sea, and thus demonstrates that, at the time of its 

 formation, the Alpine lands were free of ice up to that elevation 

 at least. Now, in many places these ancient fluviatile deposits 

 are found reposing upon glacial accumulations, and they are 

 themselves frequently obscured under masses of a similar 

 character. In the gorge of the Drance, near Thoron, the whole 

 series is admirably exhibited. At the bottom is tough, compact 

 boulder-clay, with striated stones, twelve feet thick, above 

 which come 150 feet of well-bedded river-gravel and shingle, 

 while these in turn are overlaid by an upper mass of boulder-clay, 

 charged, like the lower deposit, with erratics and highly-glaciated 

 stones. More recently, very interesting interglacial deposits 

 have been detected in the neighbourhood of Zurich. At Diirn- 

 ten and other places a bed of brown coal or lignite has been 

 worked for a long time, and was, until recent years, generally 

 believed to be of preglacial origin, from the fact that it is over- 

 laid in places with morainic debris and erratics. It has now 

 been proved, however, to be of interglacial age by the discovery 

 that it rests upon boulder-clay. The lignites have been described 

 in his usual luminous manner by Professor Heer. 1 They occur 

 at Utznach in two layers, separated by beds of gravel and fine 

 sand, and overlaid immediately by coarse shingle and gravel, 

 surmounted by erratics. According to Heer, the lignites repre- 

 sent the swampy shores of an ancient interglacial lake, which, 

 now and again overflowing its limits, deposited sediment above 

 the vegetable soil, and thus gave rise to alternating beds of peat 

 and loam, sand, gravel, etc. Among the plants which have 

 been recognised by Heer are the following : — 



Pinus abies (same as the common Swiss fir). 



P. sylvestris, Scots fir (with trunks as thick as a man's body). 



1 Urwelt der Schweiz, 2te Auflage, p. 513. 



