348 E. S. Eoicorth—The Loess. 



loose fragments broken by some means from their inner walls, but 

 no foreign substance whatever could be detected. In the remaining 

 14 specimens, while the concretions were hollow, they yet contained 

 loose particles of no substance whatever. Not a single specimen 

 was solid throughout. That they loere originally solid, or of a pasty 

 consistency, is not to be doubted, as a study of the inner surface reveals. 

 They all present a deeply fissured interior consequent on the evapora- 

 tion of water and subsequent contraction. In the vast majority of 

 cases the pyramidal masses of the interior showed distinct irregularly 



concentric lines of growth, or rather of accretion Professor 



J. D. Whitney says of them that they ' have been formed in the Loess 

 hy infiltration along the lines of cleavage and residtant chemical action 

 on calcareous matter occurring in large quantity along certain planes' " 

 The Loess of North America (American Naturalist, May, 1882, pp. 

 373 and 374). To return to the tubes. I see no evidence whatever 

 in them to support the wind theory of Professor Kichthofen, nor do 

 I see any either in the peculiar quality of the Loess, by which it 

 cleaves in perpendicular faces, which is no doubt due to the presence 

 of calcareous matter in excess, and to the presence of these very 

 tubes. Wherever we can trace current and unmistakable wind 

 formations, such as dunes, etc., etc., we have no such cleavage pro- 

 perties, and I cannot see how Baron Richthofen proposes to connect 

 them with his predicate. 



Again, the Loess for the most part is completely unstratified. 

 Occasionally, especially in America, there are local areas where 

 a kind of stratification occurs, but these are very local, and I shall 

 return to them presently. This absence of stratification I quoted 

 myself as a proof that the Loess is neither of marine, lacustrine, nor 

 fluviatile origin. It is assuredly equally a proof that it is not due to 

 gradual accumulation by the wind. Dunes accumulated by the wind 

 are so easy to study that we have no difficulty in finding materials, 

 and assuredly they present quite a diiferent structure to Loess. 

 Deposits made by wind, especially when made as Baron Richthofen 

 suggests, in dry seasons alternating with wet ones, have a laminar 

 structure corresponding to the series of layers deposited, just as de- 

 posits made by water have. Nor should we find homogeneous masses 

 several hundred feet thick with the same structure and the same 

 contents as the results of such a series of seasonal deposits. These 

 masses, to my mind, bear, on the contrary, unmistakable evidence in 

 their very structure of having been deposited by one great effort, and 

 under one set of conditions. Again, wind acting upon dust or 

 sand, deposits it with a very well-marked contour in dunes and sand 

 hills, especially when the sand is arrested by grasses (a fortiori by 

 forests of trees), and forms great masses of rolling sand hills on the 

 weather-side of any area subject to sand drifts. Where are such 

 phenomena to be traced in the structure of the Loess deposits ? No 

 doubt, in certain localities where the wind has recently and is even 

 now disturbing the surface layers of Loess, we get such wind 

 structure ; but this is purely local, and to be explained as just 

 mentioned. 



