470 Mr. Horner on the Geology of the Environs of Bonn. 



becoming charged as it rolled along with the earthy contents it afterwards de- 

 posited in the lower part of its course. We know that in the upper part of 

 the Rhine valley^ between the lake of Constance and Basle, there must have 

 existed at one time a vast freshwater lake, where the great deposits of lime- 

 stone and marl at (Eningen took place, forming a mass of horizontal beds, 

 six hundred feet thick, counting from the present bed of the Rhine. That 

 the discharge of the waters when these (Eningen beds were laid bare was 

 that which brought down the loess is, perhaps, even a conjecture too hazardous 

 from one who has never been near the spot. To give a history of the loess in 

 the valley of the Rhine, by a careful examination of its composition, organic 

 remains, its form of deposition and levels, and to trace it, if possible, to its 

 source, would be a most interesting subject of inquiry, and could not fail to 

 prove a valuable contribution to geological science. 



It was my intention to have compared this district with the great trachytic 

 eruptions of Hungary and Central France, but I found that to do so to any 

 useful purpose, I must have entered into details which would have extended 

 this paper beyond all reasonable bounds*. 



Table of Heights. 



The following heights are extracted from a Table of barometrical mea- 

 surements, by M. Moliereof Saarbruch, Civil Engineer, a manuscript belong- 

 ing to the Council of Mines at Bonn. 



The measurements are in Paris feetf , above the mean height of the surface 

 of the Rhine at Bonn, which, according to Van der Wyck, is 193 English 

 feet above the level of the sea 

 of the rock at each place. 



I have classed them according to the nature 



* See Appendix XII. p. 479. 



■\ 1 Paris foot = r0658 English; so that adding -rVth part of the height in Paris feet gives 

 very nearly the exact height in English feet. 



