of the Flints of the Upper- Chalk. 18 



merely of muddy water *. This is a very important point, as it 

 enables us to explain very many of the most striking phajnomena 

 connected with the deposit and contents and aspect of flints. 



PI. I. fig. 3 represents a specimen extracted with elaborate 

 care from the rock with my own hand, and in which therefore 

 no mistake exists as to facts oi^ appearances. It is a mass of 

 chalk in which is a flint in part enveloping a Ventriculite, though 

 a part of it (on each side of d) is an instance of a frequent case 

 above named, where the flint is found not enveloping but only 

 penetrating the substance of the animal ; and the specimen af- 

 fords the yet further illustration of a Ventriculite preserved 

 partly in flint, partly in chalk. Now this flint formerly enve- 

 loped with an extremely thin coating (not the eighth of an inch 

 thick) the lower part of the Ventriculite, together with the stem 

 and roots. After it was thus encased however, and while the 

 chalk was yet a soft mud, the flint, then necessarily solidified and 

 brittle, was by some accident broken. The force which broke it 

 nearly expended itself in so doing, and was not sufficient to 

 overcome entirely the adhesive properties of the mud and so to 

 remove the separated parts to a great distance. In this instance 

 there were in the chalk, when I found it in situ, four pieces of 

 flint a, h, e, and one at c, the impression of which last remains, 

 but the piece itself was broken out before I discovered the nature 

 of the specimen : «, h and e remain exactly as they were. 

 Neither of them has ever been disturbed, and each is perfectly 

 fixed and firm in the chalk. The chalk still remains, filling up 

 the spaces between them and between c and «, except where I 

 have, to a slight depth, cleared it away between a and h in order 

 to ascertain the interesting fact to be next stated, namely, that 

 the substance of the structure of the Ventriculite is perfectly 

 preserved and displayed in each piece a and Z>, and the edge a is 

 the exact counterpart of the edge b, and would fit to it if they ivere 

 brought in contact. A more interesting fact it has seldom been 

 my lot to develope in the course of my geological researches. 

 This case alone is sufficient to establish beyond possibility of 

 dispute the proposition to illustrate which it has been cited. 

 Neither the mass of chalk in which it now exists, nor that from 

 which it was extracted, does or did exhibit, on or near the place 

 of this fracture, the slightest trace of any movement or displace- 

 ment. Being, as above said, obviously in a state of soft mud 

 when the accident happened, it was sufficiently adhesive to retain 



* This condition, while thus demonstrated, explains with a beautiful con- 

 sistency the very frequent fact of Ventriculites, &c. preserved half in flint 

 and half in chalk. I regret that space will not allow me to enter on that 

 point, which an extensive reference to facts only may render obvious to those 

 unfamiliar with the phsenomena. 



