544 [Proc. B.N.F.C., 



siliceous organisms which abound in the strata containing beekite. 

 Given such conditions I believe that the small amount of colloid 

 organic matter present in the shells provided a medium through 

 which the silicifying waters slowly entered. The beekisation of 

 shells — greatest on the exterior and interior surfaces — corres- 

 ponds with the distribution of the organic matter in many shells. 

 The rings of beekite surrounding nuclear points mark the periodic 

 movement of the chemical action of replacement. Sollas* has 

 suggested a somewhat similar explanation of periodicity for the 

 formation of certain banded flints, but I venture to suggest that 

 beekite or cycloidal chalcedony is the first mineral which 

 definitely confesses its own history as an osmotic periodic growth. 



CONCLUSION. 



In conclusion, the following notes are added to make clear 

 certain differences between the results of Mr. Wickes' observations 

 and my own : — 



(i.) Mr. Wickes regards the formation of beekite as a 

 process which took place chiefly before sedimentation of the 

 affected fossils, and that the organic matter of the latter attracted 

 and deposited the silica while the decomposing organisms were 

 exposed to the action of sea-water. 



On the other hand I believe that the presence of shell 

 fragments (such as Inoceramus) with the broken edges beekised, 

 and single valves of shells beekised both on the interior and 

 exterior, and with an intervening layer of shell-material without 

 any sign of bore-holes, points distinctly to chemical action taking 

 place after sedimentation. 



(2.) Mr. Wickes regards the organic matter of the organism 

 as the chief factor in the deposition of the silica. In my 

 conclusions I recognise two essentially different processes at work 

 in the formation of beekite; (a) the solution of the silica of sponge 

 spicules and siliceous organisms (constructed from opaline silica) 



* Age of the Earth, p. 152. 



