Flints of the Upper or White Chalk. 201 



and eventually crush out and destroy some of their own 

 kind — their siliceous remains, no longer restrained by vital 

 forces, thenceforward becoming subject to material forces, 

 and, as suggested in a previous portion of this paper, entering 

 into colloidal combination with the protoplasm by Avhich 

 they were surrounded. Meanwhile Foraminiferal life would 

 continue to multiply in all the vacant spaces. Small patches 

 and masses of the ooze would be enveloped by masses of 

 protoplasm ; living organisms of various kinds would be 

 similarly entrapped and entombed by the closing around and 

 over them of the protoplasmic masses ; and meanwhile a 

 never-ceasing rain of minute calcareous- and siliceous-shelled 

 organisms from the surface of the ocean would fall down 

 upon the sea-bed, the protoplasmic and colloidal aggregations 

 receiving their share, and allowing these foreign bodies to 

 sink into their substance and become the bases of the future 

 pseudomorphs of the flint. 



But whilst the Foraminifera, as they died off, would leave 

 their remains on the spots where they died, and thus assist in- 

 finitesiraally, but continuously, in building up the cretaceous 

 deposit, each new brood being born, living, and dying on the 

 surface of the sea-bed, and the races*being kept up by those 

 occupying the vacant spaces, the sponges as they died off 

 would not leave their remains on the sea-bed itself, but those 

 remains would be one after the other absorbed by and form 

 part of the colloidal masses of protoplasm and silica clinging 

 together, and floating, as it were, on the immediate surface 

 of the sea-bed. This tendency of the colloidal masses of 

 silica " to adhere, aggregate, and contract,'' their viscidity, 

 immiscibility with the water^ and the extreme difficulty with 

 which they could be made to sink at all into the substance 

 of the ooze, would enable them continuously to maintain a 

 position immediately resting upon the subjacent deposit ; and 

 in this wise they would accumulate, and, by perpetual acces- 

 sions of siliceous remains from without, gradually become 

 saturated with silica. 



But even yet certain conditions would have to be fulfilled 

 before any thing like simultaneous molecular or chemical 

 action could take place over vast areas so as to produce the 

 stratification of the I'csultant siliceous masses. 



Owing to the perfect stillness prevailing at the sea-bed_, the 

 total absence of currents, the nearly constant uniformity of 

 temperature, and the perfect uniformity and constancy of all 

 the other conditions prevailing there, together with the im- 

 mense periods concerned in the deposition of the strata, there 

 is every probability that the growth of the entire series of 



