TRANSACTIONS OF THE SECTIONS. 8,7 



agriculture are confined in Northern China to the Loess, millions of people living 

 in caves dug in that earth. 



As regards the mode of origin of the Loess of China, it can neither be a fresh- 

 veater deposit, which Pumpelly supposed it to be, nor a marine formation, which 

 Kiugsmill attempted to make it — not so much on account of the absence from it of 

 either freshwater or marine fossils and the want of stratification, as because lacus- 

 trine strata could not possibly be deposited on the crests of the highest mountain- 

 ranges and the most elevated portions of plateaux, while the theory of a marine 

 origin woidd force us to presuppose Eastern Asia to have been submerged 

 at least 8000 feet beneath the present sea-level in very recent time, an assumption 

 against which there exists a great deal of direct evidence. The author next 

 attempted to prove that the Loess is a subaerial deposit, and drew attention to 

 the close similarity in the character of the surface between the Loess-basins of 

 Northern China and the salt-basins of the steppes of Central Asia. From Pamir 

 and the Karakorom to the headwaters of the large rivers fiowing towards the seas 

 which surround Asia on the north-east and south-east, a vast extent of country 

 (exhibiting diflereuces of altitude as great as any which occur in Europe) is made 

 up of numerous basins without outward drainage, the surface of each of which slopes 

 gently down from the crests or declivities of the sm-roimding mountain-ranges 

 towards the lowest portion, which is filled with a salt lake or marsh. Each basin 

 exhibits now the surface of an accumulation of debris, which smooths off the 

 inequalities of the rocks below, but is unknown equalty as to composition, 

 structure, and thickness, because no portion below the smooth surface is exposed 

 to view. Everywhere the soil is impregnated with salts, and therefore allows only 

 of the growth of a steppe vegetation. Neither the salt lakes nor the steppe 

 deposits have originated (as has been suggested) in the former submergence of the 

 whole area beneath the sea, but are of subaerial origin. The products of decom- 

 position of the mountain-ranges which constitute the skeleton of Central Asia, not 

 being able to make their way to the sea, are deposited in the adjoining basins, 

 partly by rain-water, which washes them ofl" the rocks and distributes them equally 

 over the gentle slopes, and partly by winds which carry large amounts of them 

 away and, in the present time, frequently obscure for many days the atmosphere 

 by the ingredients they carry in suspension, depositing them finally as fine dust 

 over the surface. The substances which are thus mechanically distributed over 

 the soil by either agency are retained there by the vegetation, and cause, in the 

 course of centuries, the gradual raising of the surface ; while the soluble products of 

 decomposition are mainly collected in the central pool, where the evaporation of 

 the water causes the gradual concentration of the solution ; and at the same time 

 stratified soil, similar in composition to the soil of the steppes, is deposited. If now 

 in any one basin the rains, in consequence of slight climatal changes, cause a 

 greater increase in the quantity of water than is lost by evaporation, the basin will 

 gradually be filled and the water finally seek an outlet at the lowest place of the 

 margin. With the gradual deepening of the channel the basin will be di'ained, and 

 the affluents converging towards its lowest portion will cut deep gullies into the 

 soil of the previous steppe, thus exposing its nature, and at the same time carrying 

 oft" the salts with which it was impregnated. 



A short sketch was then given of the evidence collected to show that the Loess- 

 basins of Northern China have formerly been basins without outward .drainage, and 

 were provided, each of them, with a salt lake in its lowest portion, that they were 

 gradually drained, one by one, towards the sea, and that this process, consequent 

 on slow climatal changes, is still going on along the eastern limit of the salt-lake 

 plateaux. In the Loess of Northern China is therefore exhibited the nature of the 

 subaerial deposits which fill the salt basins of Central Asia j but, the salts being 

 extracted from it, it yields all the conditions required for agriculture and the exist- 

 ence of civilized man. 



Baron von Eichthofen finally wished it to be distinctly understood as his opinion 

 that Loess may have originated in different ways, and that he does not believe the 

 theory which he has advanced as to the origin of the Loess of Northern China to 

 be applicable in every case where Loess occurs. 



