Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/519

 the Baron's description of the deposit* more than to say that in places the carbonates have segregated from the mass in nodules of fantastic shapes, which show, from the vertical position of their major axis, their subsequent origin. These nodules are of importance in a description of the mass, as, in the neighbourhood of Chinkiang at least, they seem to divide the whole formation into at

from the Report already cited (pp. 9, 10) : —
 * The following is Baron von Richthofen's description of the deposit, extracted

" The Loess is among the various substances which would commonly be called loam, because it is earthy and has a brownish yellow colour. It can be rubbed between the fingers to an impalpable powder, which disappears in the pores of the skin, some grains of very fine sand only remaining. By mechanical destruction, such as is caused by cartwheels on a road, it is converted into true loam. When in its original state it has a certain solidity, and is very porous, and perforated throughout its mass by thin tubes, which ramify like roots of grass and have evidently their origin in the former existence of roots. They are incrusted with a film of carbonate of lime. Water, which forms pools on loam, enters therefore into loess as into a sponge, and percolates it without in the least converting it into a pulp or mud. The loess is everywhere full of organic remains ; but I have never seen any other but land-shells, bones of land-animals, and the numberless impressions of roots of plants. It is not stratified, but has a strong tendency to cleave along vertical planes ; therefore, wherever a river cuts into it, the loess abuts against it, or against its alluvial bottom-land, in vertical cliffs, which are in places 500 feet high ; above them the slopes recede gradually in a series of terraces with perpendicular front faces. Where the river reaches the foot of such a wall, the progress of destruction is rapid ; the cliff is undermined, and the Loess breaks off in vertical sheets, which tumble into the stream, to be carried down by the water The beds of the affluents which join the river in these places are no less deeply cut into the Loess, and ramify into its more elevated portions like the roots of a tree, every small branch a steep and narrow gulch It gives habitation to millions of human beings They live in excavations made in the [precipitous walls of] Loess.

" As regards the mode of origin of this formation, the Loess of China, like that of Europe (where it exists on a comparatively small scale), has been supposed to be a freshwater deposit. This supposition is erroneous as regards the Loess of Northern China, because it extends equally over hills and valleys, and does not contain freshwater shells. Others have therefore considered it as a marine deposit. This view is more erroneous even than the former, because it would presuppose the whole of Northern China to have been submerged at least 6000 feet beneath the level of the sea in a recent epoch, while there is abundant evidence to prove that such has not been the case. Nor can the theory, current in Germany, that the Loess of that country was produced by glacial action, be at all applied to the Loess of Northern China, from various obvious reasons too lengthy to explain here. Unbiased observation leads irresistibly to the conclusion that the Loess of China has been formed on dry land. The whole of that vast country, which was covered by a continuous sheet of Loess before this had undergone destruction, was one continuous prairie, probably of greater elevation above the sea than the same region is now. The Loess is the residue of all inorganic matter of numberless generations of plants that drew new supplies incessantly from those substances which ascend in moisture and springs, carried in solution to the surface. This slow accumulation of decayed matter was assisted by the sand and dust deposited through infinite ages by winds. The land-shells are distributed through the whole thickness of the Loess ; and their state of preservation is so perfect that they must have lived on the spot where we now find them. They certainly admit of no other explanation than that here hinted at, of the formation of the soil in which they are imbedded. The bones of land animals and chiefly the roots of plants, which are all preserved in their natural and original position, give corroborative evidence."