DURNTEN SECTION. 151 



1 . A layer of fine yellowish sand and loam (a) . 



2. The lignite-deposit (b). 



3. A layer of pebbles several feet thick (c), in the midst of 



which was a nest of pure sand (c f ) . 



4. A layer, about 6 inches thick, of light-coloured loam, 



containing here and there nests of pebbles (d) . 



5. A thin coal-band (about 6 inches thick), composed of 



peat-plants with a few fragments of wood (e) . 



6. Loam, a thin layer (/) . 



7. Seven alternating layers of sand and pebbles (g) . 



8. On the top a few erratic blocks, originating from th'e 



Alps, and partly consisting of Alpine limestone and 

 sernifite (h). 



The thickness of the masses of pebbles and sand covering the 

 lignites or paper coals varies at very short distances, and amounts 

 here and there to 30 feet. The composition of the lignites shows 

 clearly that they originated from peat, as has been already 

 noticed (vol. i. pp. 29, 30) ; and their thickness proves that this 

 formation of peat must have gone on for very many years. 

 From time to time, no doubt, it was interrupted by inundations 

 and the deposition of fine mud, which now forms loamy bands ; 

 but it afterwards recommenced, and continued until an end was 

 almost entirely put to it by the country being covered up with 

 pebbles and sand, merely containing here and there some traces 

 of peat formation, such as is seen in the thin band of lignite 

 among beds of gravel (fig. 328, e) . 



The lignite, or paper coal, of Unterwetzikon presents the same 

 conditions of deposition as that of Diiruten. It lies at a depth 

 of from 13 to 30 feet, and is covered with masses of stratified 

 sand and gravel. Below the lignite there is a light-coloured 

 loam which contains small freshwater shells ; and beneath the 

 loam occurs a bed of gravel, in which striated fragments of lime- 

 stone, a block of granite from Pontaigles, and a boulder about 

 6 feet in diameter have been found. 



