72 H. H. Hoicorth — A Oreat Tod-Glacial Flood. 



Again, speaking of the tuff on the flanks of the Veitskopf, he 

 says : " It is perhaps in the present instance less mixed with sand 

 but more with fine clay, and hence its brighter yellow tint, its 

 more pulverulent and earthy aspect, and its still more friable and 

 loose consistence" {id. p. 60), The consistency and internal structure 

 and composition of the tufaceous mud depends in fact on the materials 

 out of which it was formed. If the rocks, instead of, as at Neuweid, 

 being of Paleeozoio age, and consisting mainly of clay-slates, etc., 

 were partially limestones, we should doubtless have a mud formed 

 from them containing large quantities of carbonate of lime. Not 

 only have we such rocks in the Rhine Valley, which are the natural 

 matrix from which one ingredient of the Loess might be derived, 

 but we have numerous calcareous springs forming travertine at 

 this very moment, and also have exhalations of carbonic acid, 

 showing the kind of material that exists below the surface. I would 

 venture, therefore, upon the theory that the Loess is in the main a 

 volcanic mud. The comminuted character of its ingredients, the way 

 in which it is highly charged with carbonates, and its distribution 

 mantling a recently active volcanic district — are positive elements 

 in its favour; while the impossibility apparently of explaining the 

 oi'igin of the deposit in any other way, and the absence so far as 

 we can judge of any objections to it on other grounds, are negative 

 factors also in its favour. I do not say that the Loess exactly as 

 we find it was protruded from the fissures or volcanic vents whence 

 it came. As we shall see, it has been very largely steeped in floods 

 of water, and has doubtless also been much mixed with the ingredients 

 of the superficial bed over which it poured. But, in the main, I believe 

 the most reasonable explanation of the difficulties that surround it 

 to be, that it is a disintegrated volcanic mud, standing in the same 

 relation to tufa that the Post-Grlacial sandstones of the Ehine Valley, 

 which have been consolidated and cemented by carbonate of lime 

 and iron, do to the loose sands of the same area dating from the same 

 period. Just as the Loess occurs in great unstratified masses, so does 

 the tufa on the Ehine — a fact which is repeatedly mentioned by Dr. 

 Ware, who makes it the subject-matter of an important inference in 

 the following sentence : " The proof that this overflow of moya was 

 a very sudden one is shown in the total, or nearly total, absence of 

 all marks of stratification " [op. cit. p. 45). There have also occurred 

 in these tufaceous deposits debris of vegetation, etc., resembling 

 those in the travertines of Bruhl, whose contemporaneity to the Loess 

 deposits is hardly questionable. On every ground known to me 

 the probability seems overwhelming that the Loess was in fact caused 

 by a vast outpouring of subterranean mud. 



The following notice of a modern outburst of such mud is not a 

 bad illustration of what probably occurred on a much larger scale 

 here. 



Near " St. Lucedo," says Lyell, " among other places, the soil is 

 described as having been dissolved, so that large torrents of mud 

 inundated all the low grounds, like lava. Just emerging from this 

 mud the tops only of trees and of the ruins of farm-houses were 



