380 PEOCEEDIIirGS OF THE GEOLOGICAL SOCIETY. [-A-pr. 26, 



terrestrial remains of easy explanation, without accepting the theory 

 of subaerial formation : a shell or other animal relic has only to drop 

 into a fissure or be carried down by a stream of water during a 

 flood ; the soil around readily adapts itself to its shape, fills its inter- 

 stices, and, in fact, in a short time loses so completely all trace of 

 having been disturbed, that the shell or other substance becomes a 

 pseudo-fossil. On the other hand, if the foreign substances were 

 really contemporaneous with the mass, they would most probably 

 be found constituting the centre of aggregation in the calcareous 

 nodules spoken of. I have broken open probably some hundreds of 

 these, and never found a trace of fossils. The Loess, as I have 

 suggested above, bears, in some respects, a mechanical resemblance 

 to chalk. These are the extreme fineness of the particles of which 

 it is composed, the presence of vertical tubes leading downwards 

 from the surface, and the occurrence of nodules like the "pot- 

 stones " in the chalk, with their major axes vertical. The large 

 amount of carbonate of lime in its composition is also worthy of note 

 in the comparison. All these reasons seem to suggest a similar 

 origin for the two formations — namely, on the bed of a tranquil sea. 



Baron von Eichthofen (T believe rightly) rejects the theory of the 

 Loess being of freshwater origin, as requiring a freshwater lake of 

 such enormous proportions that we cannot believe in its existence 

 at any period. The shape of the older mountain-chains, and their 

 peculiar weathering, he argues, forbid the supposition of glacial 

 action. (See my former paper. Quart. Journ. Geol. Soc. vol. xxv. 

 p. 137.) 



Materials of the Loess. — In stating some of my grounds for coming 

 to the conclusion that the Loess is a true marine formation, I have 

 incidentally mentioned many objections to its subaerial origin as 

 suggested by Baron von Richthofen. There are, however, others of 

 even stronger nature. Its chemical composition, consisting, as it 

 .does, mainly of silicates of alumina and of free silica in the con- 

 dition of impalpable sand, does not correspond with that of the in- 

 organic elements of plants growing on its surface. Granting, how- 

 ever, that the earthy carbonates and a portion of the sihca could be 

 derived from such a source, whence could the plants themselves 

 derive these elements, but in turn from the soil on which they grew ? 

 Lime, potassa, magnesia, iron, and silica might, then, so long as the 

 plant had access to subjacent formations, or was supplied by springs 

 from below, have been deposited in a superficial layer ; silica might 

 even, as suggested, have been conveyed by the medium of dust- 

 storms ; but whence could the silicate of alumina be derived ? A 

 superficial layer not altogether dissimilar, might, as suggested, be 

 formed so long as the plants had access to subjacent rocks. Once, 

 however, removed from contact with them, these inorganic elements 

 of the plants could only be supplied from the soil itself. Rivers are 

 inadmissible, as their action would have been to disintegrate, not to 

 build up ; springs, from the peculiarities of the . formation, cannot 

 rise to its surface. There is, finally, no known means by which 

 these inorganic matters could have been supplied from the atmo- 



