340 



On the different Beds of the White Chalk. 



Fig. 3. 



most frequently exhibited in the middle chalk, and may often 

 mislead or puzzle the observer. In this case the dislocation may 

 best be explained by describing the chalk as knotty. One of the 

 huge masses before named, when broken up, occasionally (by no 

 means always) presents a very remarkable appearance. It is full of 

 extremely hard lumps which separate readily from each other and 

 which seem as if made up of bundles of threads, — a character which 

 is often more than merely superficial. It will be clear that, as the 

 dislocation last-named could not take place without some of the 

 masses being violently compressed and distorted, when that com- 

 pression and distortion took place, the component parts of the 

 mass, according to the tenacity or cohesion of its various organic 

 contents and the varying degrees of its partial consolidation, 

 would necessarily assume the characters which are thus exhibited. 

 I have collected many interesting illustrations of these pheno- 

 mena, — having found many organic remains quite perfect as to 

 condition, but divided in the middle by one of these knots. In 

 one instance an unfortunate fish has had the fore part of his head 

 driven from its place by a knot, which, while pushing it three 

 inches forward horizontally, has pushed it two inches vertically 

 down. The striae caused by the friction are usually very clear in 

 such cases. 



Sometimes the knots assume very peculiar forms. 

 Specimens, very regularly striated, are often sold 

 by dealers as fossil wood, and the specimen here 

 figured might easily be placed in that convenient 

 group — the Coprolites. The knots in this in- 

 stance are unusually regular. Several were found, 

 one above the other, like the joints of a stem. I 

 brought away the two figured. 



As to the time at which these forces acted upon 

 the chalk, it would seem that they have not been 

 confined to any one age. As far as my observa- 

 tions extend, the dislocations above-noticed have 

 been temporary and are principally confined to 

 one bed and sera, — the middle chalk. The faults, 

 on the contrary, have been more extensive through 

 the beds. The former therefore took place before 

 the close of the secondary period and before the 

 superposition of the upper chalk. The latter must 

 have taken place at a much later period*, and we 

 are not altogether without evidence that it was 

 comparatively recent. Some time ago I obtained, 

 from the solid chalk, the well-preserved tooth of a 

 fossil horse. Without entering into any nice ques- Two-t 

 tion as to whether this belongs to the species nat. size. 

 * It is unnecessary to allude now to the cases of shivered flints in beds, 



