Insoluble Residues from the Carboniferous Limestone. 319 



3. "On the Examination of Insoluble Eesidues obtained from 

 the Carboniferous Limestone at Clifton." By E. "Wethered, Esq., 



F.Gr.S. 



The author noticed previous classifications of the Carboniferous 

 Limestone at Clifton, and submitted the following for reference in 

 the present paper : — 



Carboniferous Limestone Series. 



feet. 



Stage 0. Upper Limestones 100 



„ B. Middle Limestones 1620 



„ A. Lower Limestones : — 



1. Black Eock 490 



2. Lower-Limestone Shales 500 



990 



Total 2710 



The limestone-forming organisms in each of the above were men- 

 tioned, and the methods adopted for obtaining the insoluble residues 

 by means of hydrochloric acid were described. A table of percen- 

 tages of insoluble residues was given from the Lower Limestone 

 Shales and Black Rock, from the Oolitic Beds, Mitcheldeania-loeds, 

 and main portion of the Middle Limestones, and from the Upper 

 Limestones. 



Detrital quartz of small size, with a few grains of felspar, tour- 

 maline, and zircon, characterize the Lower-Limestone Shales, and in 

 one variety the soft tissues of organisms are represented by ferric 

 oxide, which in the case of crinoids represents the whole skeleton. 

 Residues of the Black Bock exhibit slight secondary crystallization 

 round detrital quartz, whilst amorphous and chalcedonic silica 

 become more plentiful. Residues of the Middle Limestone consist 

 to a less extent of detrital quartz along with micro-crystals of 

 quartz, amorphous and chalcedonic silica, and less frequently of 

 pyrites, tourmaline, and zircon ; sponge-spicules are also noted. 

 Towards the top of the Middle Limestones the proportion of detrital 

 quartz increases and the deposit of secondary silica on the surface of 

 quartz grains is less marked. 



The nature of the amorphous and chalcedonic silica in the lime- 

 stone, and the relations of this silica to the small quartz crystals, 

 were also discussed. The latter were shown in some instances to 

 possess nuclei of detrital quartz, and where this is not the case, to 

 have resulted from the crystallization of amorphous silica. 



February 29.— W. T. Blanford, LL.D., F.R.S., President, 

 in the Chair. 



The following communications were read : — 

 1. " An Estimate of Post-Glacial Time." By T. Mellard Reade, 

 Esq., C.E., F.G.S. 



The author showed that there exists on the coasts of Lancashire 



