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I 



true form of the enveloped fossil. In geological formations there 

 is an alternation of porous and non-porous beds, organic remains 

 are more abundant in the latter, owing to the animal structure 

 having been dissolved out of the percolating water in the f(mncr. 

 Many sandy beds are thus destitute of fossils. Tabular flint is 

 often found associated with a non-porous bed, the dissolved silica 

 gravitating from above being arrested and consolidating. 



The tabular banded flints found at the top of the chalk at the 

 junction with the Thanet beds, are produced by the chalk having 

 been stratified with alternate thin beds of porous chalk, and more 

 argillaceous layers. The flinty structure is sometimes absent, a 

 very granular chalk still remaining, then from the under surface 

 of the flint above may be seen smaU. stalactital points invading 

 the chalky space thus undergoing silification. An opaque white 

 band repesents the chalky layer, making these flints often resem- 

 ble onyx-stone. 



The nodular banded flints have a close alliance with the banded 

 structure of agates, the opaque portions in both are most porous. 

 In the process of silicificatiou, the silica appears to be alternate- 

 ly more and less crystalline when deposited, or the bands may be 

 formed by replacement of endogenous depositions within the 

 geode. The banded structure in flint is generally associated 

 with some cavity which is fiUed with chalcedony. A geode 

 having in its centre beautiful crystals of amethyst was exhibited 

 to demonstrate the banded structure formed from within. 



The condition of the recemented flints alluded to in connection 

 with the junction bed of the chalk and the Thanet Sand pointed 

 to a more rapid formation of flint, the result of a greater propor- 

 tion of silica in solution probably derived from the sandy beds 

 above, and perhaps separated by a process of natural dialysis 

 yielding gelatinous or " colloidal" form. The peculiar moulded 

 form these flints take aj)pears to confirm this. 



So remarkably is flint associated with limestone, that when 

 carbonate of lime is very abundant in Tertiary sandy beds, the 

 fossil shells which constitute the limestone are converted into 

 flint or or become silicified. 



It may then finally be concluded that flint stones are a 

 chemical product formed in the laboratory of Nature, that they 

 often and indeed generally are associated with some organic 

 substance, which in the fir.st instance formed the nucleus round 

 whiih the Silica gathered, but that organic substance need not be 

 present. 



The cordial thanks of those present were accorded to the 

 President for his very interesting lecture and wishes were ex- 

 pressed that the subject might be taken up at some future tinia. 



Mr. Sidney Harvey explained the apparatus and process used 



