84. 



twenty-six aquatic. The author infers that if the waters of the 

 Rhine were now received into a lake, the sediment of such a lake 

 might contain more terrestrial than aquatic shells. 



After some observations on the hollows and furrows in the gravel 

 of the Rhine which have been filled with loess, the author states 

 that the interior of the crater of the volcanic mountain called the 

 Roderberg is in great part filled up with pure loess, which was 

 pierced to the depth of 65 feet in digging a well in 18S3. But 

 although this and other sections prove the posteriority of the loess 

 in general to the volcanic formations of the Eifel, Mr. Lyell ad- 

 mits that at Andernach there have been considerable falls of pumice, 

 scorice and volcanic sand during the period of the formation of the 

 loess. In proof of this, the sections in the Kirchweg near Ander- 

 nach, are described. 



The loess is then stated to be spread almost everywhere over the 

 tertiary and secondary strata around Mayence, Oppenheim, Alzey, 

 Flonheim, Eppelsheim and Worms. There is a section of loess 

 with shells, alternating several times vvith gravel, at the Manheim 

 gate of Heidelberg. 



The loess between Heidelberg and Heilbronn appears to attain 

 the height of seven or eight hundred feet above the sea. In this 

 district, shells of the Succinea elongata alone are so abundant as to 

 exceed in number all the accompanying land shells. The author 

 then mentions the loess near Stutlgard and between Goppingen and 

 Boll in Wurtemberg. He found no traces of it in the course of a 

 tour by Heidenheim, Solenhofen, Nuremberg, Bayreuth, and the 

 cave district of Miiggendorf, but he found it again between Bam- 

 berg and Wurtzberg in the valley of the Mayne. It was wanting 

 in the Spessart and the country around Aschatfenberg, but is abun- 

 dant near Frankfort and in several parts of Nassau. In the valley of 

 the Lahn near Limburg, it contains its usual shells and alternates 

 frequently with gravel. 



From these facts and others mentioned in the paper, the author 

 deduces the following conclusions: — 



First, That the loess is of the same mineral nature as the yellow 

 calcareous sediment with which the waters of the Rhine are now 

 commonly charged. 



Secondly, The fossil shells contained in the loess are all of recent 

 species, consisting partly of land and partly of freshwater shells. 



Thirdly, The number of individuals belonging to land species 

 usually predominates greatly over the aquatic, and this scenes now 

 to be the case with the modern shells drifted down by the Rhine. 



Fourthly, Although the loess when pure appears unstratified, it 

 must have been formed gradually, as the shells contained in it are 

 numerous and almost all entire, and beds of shelly loess sometimes 

 alternate with strata of gravel or volcanic matter. 



Fifthly, Some volcanic eruptions must have taken place during 

 and after the deposition of loess. 



In conclusion, the author states that great changes must have oc- 

 curred in the physical geography of the basin of the Rhine since 



