110 Mr Lyell cwi the Loaviy Deposit of the Rhine. 



I conjectured that its height was about 600 feet above the level 

 of the Rhhie. 



From Andernach I proceeded to Neuwied, and from thence 

 across a plain covered with pumice to Sayn. Near the latter 

 place, I saw the loess forming a terrace on the flanks of the hills 

 composed of greywacke, and at a lower level the country is 

 covered with volcanic ejections, which, according to M. von Oeyn- 

 hausen, are clearly seen in some sections to overlie the loess, a 

 facj: which I had not time to verify. 



From Sayn I proceeded to Mayence, where the country on 

 the left bank of the Rhine is composed of tertiary limestone, 

 with green and white marls. This formation is overtopped by 

 loess, and both are cut off abruptly in the escarpment which the 

 high land presents towards the Rhine at Mayence, Oppenheim, 

 and other places. 



The tertiary formation must here have undergone consider- 

 able denudation since the loess was superimposed. In an ex- 

 cursion through part of the Duchy of Darmstadt by Mayence, 

 Oppenheim, Alzey, Flonheim, Eppelsheim and Worms, I 

 found the loess spread almost everywhere over the country, and 

 the inferior tertiary strata and secondary red sandstone only ex- 

 posed to view in valleys, or where the country begins to rise' to- 

 wards the base of the Donnersberg. 



At Heidelberg Professor Bronn, who has devoted much time 

 to the study of the loess, told me that he is persuaded that the 

 loess was not formed suddenly by a transient flood, but gradu- 

 ally by successive deposition. The absence of all appearance of 

 stratification, which formerly led me and others to a different 

 conclusion, is owing, he thinks, chiefly to the homogeneous na- 

 ture of the loamy deposit. In some places he has seen calcare- 

 ous concretions forming horizontal lines, marking the greater 

 quantity of calcareous matter which was thrown down when 

 some of the layers were accumulated. I had formerly imagined 

 that the loess must have subsided suddenly from a flow of 

 muddy water, like the Moya of the South American volcanoes, 

 in the same manner as I believe the unstratified trass of the 

 Rhine volcanoes to have been formed ; but I am now convinced 

 that Profess )r Bronn's view of the subject is more correct. 

 Among other places, the signs of successive deposition are well 



