268 Notices of Memoirs — Geology. 



displacement or by contraction of tlie surrounding clay ; quartz was 

 then deposited on the Avails of the cavities, as a thin layer of crystals, 

 having their apices directed inwards ; and, finally, a solution of 

 chloride of sodium was introduced into these drusy cavities, which 

 thus became gradually filled by a second deposit of salt. There are 

 reasons for supposing that in most cases the original cube of rock- 

 salt was not completely removed, but that a fragment remained in 

 the cavity, and served as a nucleus for the second deposition. 



The pseudomorphs of rock-salt after carnallite occur chiefly in a 

 bed of clay immediately below that which yields the other pseudo- 

 morphs, but in some cases the two kinds are associated in the same 

 bed. The crystals present forms characteristic of carnallite, and are 

 coloured red by the presence of ferric oxide. 



The following analyses show the composition (I.) of the white 

 pseudomorphs after rock-salt, and (II.) of the red pseudomorphs 

 after carnallite. The salts were dissolved in water, with addition 

 of a little nitric acid ; the insoluble residue consisted chiefly of silica, 

 with a small proportion of ferric oxide and alumina. 



I. II. 



Residue 16-92 4-24: 



Chloride of Sodium 63-71 90-35 



Sulphate of Calcium • 8-97 1-46 



„ Sodium 2-94 0-24 



,, Magnesium 1-66 1-04 



Ferric Oxide and Alumina 0-92 0-83 



Loss (water) 4-88 1'84 



100- 100- 



r. w. E. 



Brief Abstracts — B. Geology. 



2.— Taylor, J. E. A Sketch of the Geology of Suffolk. From White's 

 History, etc., of the County, pp. 13. Large 8vo. Sheffield, 1874. 

 An account of the literature of the subject is first given, and then 

 the geological formations are described, in ascending order, beginning 

 with the Chalk, the places where it crops out being noticed, and also 

 the various depths at which it has been foimd in wells. The Reading 

 Beds and London Clay follow next, and many sections are named. 

 The "Box Stone Deposit" is then described; it underlies the 

 Crag, and is characterized by containing many large flints, foreign 

 boulders, and brown water-worn sandstone masses, which last often 

 contain casts of shells, that ai-e disclosed by a sharp blow ; and it is 

 now concluded that these stones are the remnants of a deposit older 

 than the Coralline Crag, to which thej were once thought to belong. 

 The peculiar Suffolk formations. Coralline and Red Crags, with their 

 chief sections, are noticed, and followed by accounts of the Norwich 

 Crag, Chillesford clay and Forest-bed, a description of the sandy 

 gravels and clays of the Lower and Upper Glacial Drifts and of the 

 Post-Glacial beds concluding the essay. W. W. 



^ The sulphates are calculated as anhydrous salts. 



