138 . Reports and Proceedings— 



Geological Society of London. 

 I.— January 9th, 1895.— Dr. Henry Woodward, F.R.S., President, 

 in the Chair. The following communications were read : — 



1. ^' The Formation of Oolite." By E. B. Wethered, Esq., F.G.S. 

 In previous communications the author has described pisolites 



formed by the growth of Girvanella, and some true oolitic granules 

 having a like origin. He has long entertained the opinion that all 

 oolitic granules are of organic origin, but has not, up till now, been 

 in a position to prove this. 



He describes the form of the grannies, which frequently exhibit 

 a series of concentric layers of calcium carbonate around a nucleus, 

 and also dark striee and patches, the former placed more or less at 

 right angles to the nucleus. The concentric layers often exhibit an 

 irregularity which the author maintains to be incompatible with 

 their clieraical origin, and he considers that each layer represents 

 tubular forms of growth. Again, granules are found made of 

 calcium carbonate occurring in two forms — a vitreous portion 

 repi'esenting the organic structural part, and an amorphous portion 

 consisting of ordinary carbonate of lime, which is either infilling or 

 secreted material, possibly both. 



In discussing the origin of the crusts around the nuclei, the author 

 treats of the radial structure which is so marked a feature in the 

 crust of oolitic granules. This structure has the appearance of light 

 and dark striai when seen by reflected light : the light ai'e tubules 

 which have grovyn at right angles to the nucleus, whilst the dark 

 are secondary formations. 



He refers to Rolhpletz's description of the oolitic granules of the 

 Great Salt Lake, which are stated to have originated from the 

 growth of lime-secreting alg^, and thinks it possible that the fossil 

 forms are of like origin, though not necessarily due to organisms 

 allied to algee, and possibly even lower in the scale of life ; Gir- 

 vanella was the first type of oolite-forming organism discovered, and 

 it is simply a tubule. 



2. '• On the Lias Ironstone around Banbury." By Edwin A. 

 Walford, Esq., F.G.S. 



The ferruginous limestone of the Middle Lias of the Banbury 

 district occurs practically within a ten-mile circle around Banbury; 

 The stone (the Marlstone of the Geological Survey) is an "oolitic" 

 cyprid-limestone with much molluscan and crinoidal debris and 

 some quartz-grains. The author describes the lithological characters 

 of the rock, and their variations, as traced laterally and vertically, 

 giving a full description of its local development, with detailed 

 account of the sections in the principal exposures. The marlstone 

 of this area is dissimilar from that of Gloucestershire both in 

 appearance and in fossil contents, the Gloucestershire stone being of 

 earlier deposition and representing better the base of the Banbury 

 series, rather than the stratum which is richest in iron. From the 

 blue .clays of the margaritatus-zon.e up to the rock-bed itself there is 



