10 Mr. Toulmin Smith on the Formation 



there is no doubt, as already seen, of sponges being, like other 

 remains, sometimes inclosed in flint : the point is to explain upon 

 a general and universally applicable principle, the presence, in all 

 its forms, of flint; and this has been seen by the extract already 

 given to be the express intention of Mr. Bowerbank. If there- 

 fore it appears that it is impossible, in any one particular in- 

 stance, to explain the presence of flint on this theory, the theory 

 itself falls wholly to the ground as an explanation of the phseno- 

 mena. Its insufficiency is not any more demonstrated, though 

 it is further illustrated, by multiplying such instances or sets of 

 instances. Such illustration is afforded by the variety of facts which 

 have been already cited, and the citation of which, did space per- 

 mit, might be extended almost without limitation. It is conceived 

 however that it has been sufficiently shown, first, from the con- 

 dition of the assumed sponge remains themselves, second, from 

 the nature and condition of the inclosed organic bodies, that the 

 sponge theory is in nowise tenable as a comprehensive theory 

 to explain the origin of the forms and modes in which flint is now 

 found in the chalk. 



We will now take another ground apart from any internal ex- 

 amination, to which we have hitherto confined ourselves, of the 

 substance of the flint. And we shall find, on taking a careful 

 review of some facts of the external forms and modes in which 

 the flints are found, that the sponge theory is not only wholly 

 unsatisfactory, but absolutely impossible ; while we may gain some 

 hints as to the true origin of these masses. To avoid extending 

 these remarks to too great a length I shall confine myself to a 

 few cases, which however are conclusive, and all of which, with 

 many others confirming them, have been collected by myself upon 

 the spot ; and I purposely select such as have been collected at 

 spots many miles apart. 



The reader is requested to examine carefully the specimen 

 represented in fig. I of Plate I., which is, with the others there 

 figured, of the natural size. It will be seen that the external 

 surface of this specimen is entirely covered with strong liny 

 ridges. These ridges overlap one another precisely like pieces 

 of card-board cut to a clear square edge, or, to take another and 

 I believe an exact analogy, as flakes of ice just on the point of 

 congelation would do if violently agitated*. They rise one above 

 another about, on an average, the twentieth of an inch, and, as it 

 will be seen that they run in various directions, they thus give to 

 the surface a very peculiar form, the anticlinal axis b c crossing- 

 it, and there being at «, where the ridges run concentrically, a 

 deep and very accurately rounded cup, of which a small space at 



• In an experiment with Glauber salts, made since the above was written, 

 I found, on an accidental motion given, exactly the same character of ridges 

 assumed. ^ 



