544 Geological Society: — 



the accepted classification of the deposits) be considered to belong 

 to the Gault. The fossils constitute the newest Lower Cretaceous 

 fauna as yet recognized in England. Several species, hitherto 

 supposed to be confined to the Selbornian, are now shown to have 

 been in existence before the deposition of the Gault. The litho- 

 logical characters of the bed indicate a sea-bottom of moderate 

 depth, swept by powerful currents, and the conditions were thus 

 similar to those which persisted in the neighbourhood throughout 

 Lower Greensand times. The overlying Gault shows a change to 

 more tranquil waters, probably of greater depth. 



Pebruary 25th.— Prof. Charles Lapworth, LL.D., E.R.S., 

 President, in the Chair. 

 The following communications were read : — 



1. ' On the Occurrence of Dictyozamites in England, with Remarks 

 on European and Eastern Eloras.' By Albert Charles Seward, 

 Esq., M.A., E.E.S. 



2. ' The Amounts of Nitrogen and Organic Carbon in some Clays 

 and Marls.' By Dr. N. H. J. Miller, F.C.S. 



Analyses of soils are given to show that, under most conditions, 

 decaying vegetable matter in soil tends to become more nitrogenous, 

 on account of the greater ease with which gaseous compounds are 

 formed with carbon than with nitrogen. Hilgard's experiments 

 throw light on the effects of extreme conditions of climate, the 

 amount of soluble humus being much greater in soils in humid than 

 in arid climates ; thus, although the total amount of soluble nitrogen 

 does not vary much, the percentage of it in the humus varied very 

 considerably in the two cases. The large areas of peat-land known 

 as ' Hochmoor ' contain larger proportions of carbon and nitrogen at 

 depths of 7 and 14 feet than at the surface. The organic matter of 

 soils is of two kinds — the humous portion and the bituminous : the 

 latter being regarded as belonging to the original deposit from which 

 the soil is derived. Analyses of soils and subsoils are given to 

 illustrate this point. Eurther light on this subject is derived from 

 the analysis of a series of specimens from the following deposits, 

 obtained through the kindness of Sir Archibald Geikie from borings 

 in the x^ossession of the Geological Survey: — Lower Lias, Oxford 

 Clay, Kimmeridge Shale, Purbeck and Wealden strata, Gault, Chalk- 

 Marl, and London Clay. Apart from the interest due to the great 

 depths from which the samples were obtained, and the evidence which 

 they afford of the enormous accumulations of combined nitrogen, they 

 possess the further and greater value of representing the materials 

 out of which large areas of soils have been derived. Calcium- 

 carbonate varies from 82-1 to per cent., organic carbon from 

 1-229 to 0-229, and nitrogen from 0-068 to 0*021 ; the highest pro- 

 portion of carbon to nitrogen is 40-3 to 1, and the lowest 8-9 to 1. 

 It would be important to determine, in the case of these older 

 deposits, whether any of the organic matter at all is in the form of 

 humus. 



