of the Flints of the Upper Chalk. 15 



the soft chalk-mud upon another mass at that moment on the 

 point of sohdifying. The movement which caused this fracture 

 and impelled the pieces onto the yet fluid mass was probably 

 the same which caused the whole surface on which the fractured 

 pieces alighted to slip forwards, and which surface and the mass 

 beneath it, probably by the very agitation thus caused, instantly 

 solidified, leaving the ridge a b, and fixing the fractured pieces 

 firm. 



This case illustrates and demonstrates all the conditions al- 

 ready noticed; extreme liquidity and rapid solidification of the 

 flint, together with the soft state of the surrounding chalk. 



It is unnecessary to enter now into further details of facts, or 

 to dwell long on the conclusions to which the numerous facts 

 above cited lead us. Some of these conclusions have been sug- 

 gested in the course of these observations, others will naturally 

 suggest themselves *. Numberless facts unite to show that the 

 sponge theory is wholly untenable, while they point to a state of 

 facts easily conceivable and analogous to what is found in other 

 formations ; which is in accordance with known laws and experi- 

 mental phsenomena ; and with which all the observed phsenomena 

 of flint will be found consistent. For different mineral concre- 

 tions to form themselves round organic centres, by the combined 

 efiect of some affinity thereto and of their own molecular attrac- 

 tion, is a phaenomenon of frequent occurrence. In the Septaria 

 of the London clay, each having its organic centre, numerous 

 organic remains are found interspersed, and frequently half im- 

 bedded and half projecting on the surface, precisely as is the 

 case with the flints. The siliceous solution, which was probably 

 supplied periodically only, being supplied but to a limited ex- 



* I conceive it unnecessary to enter here at length on the question of the 

 arrangement of the flints in layers. Such a phaenomenon presents no 

 greater difficulty than any fossiliferous layers proving several distinct and 

 successive hottoms of the sea ; such, for example, as form so marked a 

 feature of the Dudley limestone. Tliere would thus always be some bottom 

 sufficiently hard to resist the pressure caused by the specific gravity of the 

 siliceous fluid and flints, the greater part of which would thus fall onto it 

 through the softer mud above. Scattered small flints are found between 

 the layers, which a variety of causes may have arrested in their descent. 

 The distances between the layers are by no means equal ; the modifying 

 conditions which caused at intervals, in this formation like others, a rela- 

 tively hard bottom to form, varying at different times. That such "modi- 

 fying conditions" must be taken into consideration will be evident from the 

 important facts that in the LowerChalk no flints at all occur in the south-east 

 of England, while in the Middle Chalk they do occur scattered indiscri- 

 minately through the mass ; but it is only in the Upper Chalk that they 

 assume the peculiar stratified arrangement which marks it. To explain 

 these facts on the sponge theory would indeed be impossible, but they are 

 perfectly consistent with the conclusions above drawn, and those conclusions 

 and these facts mutually illustrate each other. 



