444 /. C. Mansel-Pleydell^Geology of Dorset. 



passed tlirougli a district of granitic and sj^enitic rocks which 

 iDrought down these pure kaolin clays. The coarser materials and 

 qnartzose grits were probably drifted from their original position 

 either by periodical or intermittent floods. 



The occurrence of isolated Tertiary patches resting here and 

 there on the Chalk, of which the one at Tollard Eoyal is furthest 

 from the central mass, leads to the supposition that denudation has 

 removed the large masses which intervened, and, as has been already 

 hinted, probably extended far over the Chalk below. 



The heaths of Bere Eegis, Affpuddle, and Piddletown, are here 

 and there pitted with circular conical hollows, resembling the upper 

 portion of an hour-glass ; they vary from 60 to 80 yards in circum- 

 ference ; the largest is 280 yards round. They are supposed to be 

 swallow-holes, the result of the dissolution of Chalk by means of 

 the carbonic acid contained in the rain-water, and the subsidence of 

 the superjacent sands into the resulting hollow causing a depression 

 of the surface like that which takes place in the sands of an hour- 

 glass soon after it has begun to run. The Eev. 0. Fisher considers 

 that the formation of these pits was subsequent to the outspread of 

 the superficial gravel. 



Superficial Gravels, etc. — Gravels and Brick-earths cover the 

 surface of the heath-lands, as well as large portions of the Chalk and 

 the Oolites, on the border-lines of the Vale of Blackmore. 



The High-level Gravels are all rounded by water-action, and 

 originate from beds of which we have fragmentary traces in several 

 parts of the county, but which do not now exist nearer than Corn- 

 wall, porphyry, granite, and quartz being their constituent parts ; 

 they cover the table-land between Bournemouth and Poole, which 

 forms the eastern extremity of the extensive tract of land of which 

 Picket Plain and Ochnell form the northern boundary, and were 

 probably spread out previous to the wearing away of the surface of 

 the present existing valleys. The lower gravel-beds are represented 

 largely throughout the county, not only covering the deep combes 

 which intersect the coast-line, but lie at the base and sides of many 

 of the inland valleys. Those of the Stoiir and Piddle have yielded 

 remains of Elephas primigenius and BJdnoceros tidiorliiniis ; at Gains 

 Cross near Durweston tusks of the former and teeth of the latter 

 were met with in the railway-cutting in a bed of flint-gravel 60 feet 

 above the river. Mr. Shipp (of Blandford) has a good collection of 

 the remains of these pachyderms, from a pit in the nursery-gardens 

 between the town of Blandford and the turnpike-gate on the Dor- 

 chester road ; molar teeth of Elephas primigenius were found some 

 years ago at Dewlish, in a tributary of the river Piddle. The Avon 

 too has yielded elephants' teeth in gravels 40 feet above the river. 

 Elephant, Bison, and Deer remains were exhumed from a bed of 

 gravel at a combe at Encombe, the seat of the Earl of Eldon. 



There are evidences of man's occupation in the cliffs near Bourne- 

 moTith in the occurrence of flint implements among the gravels 120 

 feet above the sea-level. Owing to the absence of organic remains, 

 it is impossible to decide as to the origin of these gravels, whether 



