R. H. Hoioorth — A Great Post-Glacial Flood. 71 



of the Smitlisonian Contributions to Knowledge, and speaks at some 

 length in reference to the volcanic strata of Southern Mongolia. 

 Speaking of the Shamo Desert and its borders, he says : " The 

 volcanic rocks of Lake Baikal and of the region to the east, the 

 occurrence of products of this class in place and as scattered 

 fragments at many points on the route across the plateau, and 

 finally the information derived from Chinese authorities concerning 

 the existence within historical times of active volcanos, among the 

 mountains of Manchuria to the east and in the Tien-shan of the west, 

 all point to a development of volcanic activity, which was formerly 

 coextensive with the area of the present table-land. The remains 

 of this action make themselves felt in the violent earthquakes that 

 from time to time shake the districts of Northern Chihli and the 

 shores of Lake Baikal " {op. cit. pp. 75, 76). The mountains that 

 border the Mongolian desert on the south are full of traces of recent 

 volcanic action, and seem as closely connected with and to be as 

 much the focus of the distribution of the Loess as those of Central 

 Europe. This clue, in the absence of others, is assuredly worth pro- 

 secuting. Can it be that the Loess, which we have seen many reasons 

 to doubt having been of either subaqueous or subaerial origin, may 

 be of subterranean origin ? This somewhat paradoxical proposition 

 may not seem so extravagant when examined a little more closely. 



Mr. Steininger and Dr. Hibbert-Ware have shown that the Rhine 

 volcanos, when active, poured out an immense quantity of mud, 

 which has been consolidated into tufa ; and the latter expressly com- 

 pares them to the mud volcanos or moyas of the Western World 

 described by Humboldt. This mud is formed from the volcanic 

 sand or ash, which is itself the product of the destruction of the 

 subjacent strata, and whose chief characteristic is its extremely 

 comminuted character and minute state of mechanical division (which 

 is one of the peculiar features of the particles which form the Loess 

 itself). This state of minute division, as Dr. Hibbert-Ware says, 

 makes it easy to form a paste out of the dust when it is mixed with 

 water. He attributes the formation of the various tufas which occur 

 in the district which he describes " to the boiling tufaceous mud, or 

 moya, which once filled, even to an overflow, the valley of Rieden " 

 (op. cit. p. 40). The occurrence of this mud in various districts of the 

 Rhine volcanic area is pointed out in many passages by Dr. Hibbert- 

 Ware. Its density and composition differ with the materials out 

 of which it has been formed, and the character of the adjacent 

 rocks, and in some cases has been considerably altered. Thus, 

 Dr. Ware describes how, by the action of water, "the substance 

 of the tufaceous mud would be so intimately blended with the 

 fine sand and plastic clay (as at Neuwied) as to assume a less 

 firm consistency^ which at the present day is indicated by the 

 rapidity with which the mixed deposit is disintegrated ; particularly 

 by the action of rains. But although the tufa is thus disguised, its 

 origin, after a little experience, may be easily recognized, owing to 

 the yellow or brownish colour and pulverulent, yet harsh feel, which 

 it continues to preserve" (Hibbert-Ware, op. cit. p. 43). 



