CHAPTEE XIV. 



RETROSPECT OF THE OOLITIC SYSTEM. 



THE circumstances under which the great tripartite system of 

 oolitic deposits took place are sufficiently varied in detail, and often 

 enough repeated in successions of similar events, to encourage an 

 attempt to treat the whole with reference to some general laws 

 which may he accepted as at least approximately true. The 

 physical conditions of deposit having been in this manner con- 

 sidered, the series of oceanic life may become the subject of further 

 generalization. 



First, then, we remark in the whole oolitic system, from the 

 base of the lias to the top of the Portland rock, no remarkable even 

 local derangement of the parallelism of deposits, so that violent 

 movements during the whole long period under review, though 

 they may have happened elsewhere, could have had no special 

 influence in this comparatively tranquil sea-basin. Yet that both 

 limited upward, and especially extensive and continued downward, 

 movement occurred will be manifest on considering certain phse- 

 nomena. That dry land subject to inundations was at no great 

 distance during the whole period, is evident by the not infrequent 

 occurrence of drift-wood in all parts of the series of strata ; but 

 the actual inflow of rivers is not to be put in clear evidence, though 

 lagoon laminations or estuarine accumulations may be inferred both 

 at the base of the lias and the top of the Portland, as well as in 

 the Stonesfield, Collyweston, and Poulton slates. 



A conglomerate can hardly be quoted in the whole of this oolitic 

 series of the midland; only rarely any mark of approach to the 

 ancient shore, though one such has occurred to me in the brow 

 of a hill at the edge of the oolite on the Chipping-Norton road 



