■580 DB. J. W. EVANS ON MECHANICALLY-FOKMED [Aug. I9OO, 



where the oolitic character is strongly developed, the larger fossils 

 are almost entirely absent. 



I have recently had the opportunity of examining some of the 

 false-bedded strata in the Great Oolite near Cirencester. They 

 are well seen in the quarry in Hare Bushes Wood, east of the 

 town. 1 Here two series of false-bedded strata occur, separated by 

 beds showing the true stratification. There are no fossil-fragments 

 which could not have been easily transported by a moderately strong 

 breeze. The false-bedding dips at an angle of about 20° north- 

 eastward. As the true dip is very slight, the inclination and direction 

 of the bedding-planes represent, approximately, the original dip of 

 the false-bedding ; so that if these strata are of seolian origin, they 

 afford evidence that the prevalent winds blew from the south-west, 

 as at present. Microscope-sections of the upper false-bedded strata 

 showed the clear calcite-matrix and other characters distinctive of 

 the Kathiawar and West-Indian rocks : the oolite-structure was 

 not, however, quite so well developed as in the Bahamas rocks. 

 Microscope-sections from the quarry by the cross-roads south-west 

 of Baunton Downs, [46] p. 284, north of Cirencester, showed some- 

 what similar characters. Throughout the district the prevailing 

 dip of the false- bedding is north-easterly. 



Through the kindness of Mr. Teall, I have had an opportunity of 

 examining numerous microscope-sections of the rocks of the Great 

 Oolite in the possession of the Geological Survey of the United 

 Kingdom. Many of these are in every way similar to those that I 

 have described from the neighbourhood of Cirencester, and to the 

 SBolian rocks of the West Indies and Kathiawar. The worn character 

 of some of the grains 2 suggests abrasion by wind-action. Siliceous 

 sand-grains only occur occasionally, and are seldom well-rounded ; 

 but that is to be expected on the shores of a coral-island composed 

 almost entirely of calcareous material, as it is of course the mutual 

 friction of minute particles of silica and equally hard rock-masses 

 in desert- areas which effects the rounding. 



The false-bedded Oolites which succeed the Stonesfield Slates with 

 their turtles' eggs, and the ' decidedly oolitic ' freestone with oblique 

 bedding that overlies the Oolithes-bathonicus Bed in the upper part 

 of the Great Oolite, are therefore not improbably of seolian origin ; 

 and the Great Oolite Series, from the Stonesfield Slates to the Forest 

 Marble, would appear to represent an alternation of littoral and 

 subaerial deposits, with occasional intercalation of shallow-water 

 marine beds. The markedly lenticular character of the more oolitic 

 beds is in accordance with this view. 3 



1 They occur at an horizon which has been included by Prof. Hull in 

 the Forest Marble. This quarry is in the wood north of the main road, and 

 is distinct from the Hare Bushes Quarry south of the road in which, I believe, 

 the reptilian eggs were found ; see also [46] p. 284. 



2 See [44] p. 83, and Mr. Chapman's paper, pp. 584-85 of this volume. 



3 See [46 1 pp. 248-49, 250-59, 271 & 290. These calcareous asolian strata 

 were probably accumulated under conditions more closely allied to those which 

 obtain in the case of the calcareous dunes of coral-islands, than to those of the 

 deposits in the more hilly parts of Kathiawar and Kach. 



