Vol. 60.] IGNEOUS ROCKS OF THE BRISTOL DISTRICT. 147 



blocks. The fragmental beds are here found above the lava, but 

 there is an interval in which there is no exposure. They consist 

 of a reddish ashy limestone and a thinly-bedded, greenish, ashy and 

 gritty limestone, coarser below and finer above, in which oolitic 

 granules occur plentifully. 



(6) The more easterly exposure affords perhaps the most 

 characteristic and convincing section of ashy beds in the district. 

 The lenticular bands of coarse greenish tuff, the limestone-inter- 

 calations, the close admixture of lapilli, limestone-fragments, and 

 oolitic grains, the whole appearance of the 13 or 14 feet of rock 

 exposed in a vertical mural face are stamped with the hall-mark of 

 submarine volcanic action. The beds seem to cross the track 

 about 200 yards to the north-west, as it ascends the hill near an 

 orchard. No lava occurs in situ here ; but a remarkably-fresh 

 olivine-dolerite is abundantly found in small blocks (among which 

 are some of breccia) scattered over the field to the west of the 

 main exposure. It may therefore be inferred, since the dip is 

 easterly, that the lava closely underlies the breccias and tuff's, as 

 in the other Goblin-Combe exposure. 



(6) Near Cadbury Camp. 



Beyond the occurrence of fragments of ' trap ' thrown out from 

 rabbit-burrows in Wood Lane, at the angle between Round Wood 

 and St. John's Wood, we have found no indication of the exposures 

 marked in Sanders's map. There is nothing to show whether or 

 not the trap is contemporaneous. 



III. The Approximate Horizon of the Igneous Rocks. 



In the ' Summary of Progress of the Geological Survey' no attempt 

 is made to assign to the volcanic rocks any definite place in the 

 stratified series which constitutes the Carboniferous Limestone. 

 In 1898 one of us stated, in the British Association Handbook 

 (Bristol Meeting), that the Middle Hope beds were of an age 

 slightly anterior to that of the band of oolitic rock which occurs 

 at the foot of the Gully in the well-known Clifton section : and, 

 from observations made in 1894-95, he had tentatively assigned 

 to the Spring-Cove lava a position about ]50 feet below this oolitic 

 band. In endeavouring to work out the position of the volcanic 

 series with greater precision we have had the advantage of much 

 palaeontological assistance from Mr. Arthur Yaughan, B.Sc, F.G.S., 

 who is engaged on the zoning of the Carboniferous Limestone 

 of the district under consideration. We tender him our hearty 

 thanks for his ungrudging assistance. He has supplied for our 

 guidance, and allows us to quote, the following table, wherein certain 

 broadly-marked horizons which bear on the subject in hand are 

 indicated : — 



l 2 



