364 : MR J. D. FALCONER ON THE 
to include the Bo’ness coalfield and its intercalated volcanic rocks. In one sense, there- 
fore, since mere thickness of strata is in this case no index to rate of deposition, the 
whole of the Bo'ness coalfield may be considered the equivalent of the lower Bathgate 
coalfield. On the other hand, from the position of the igneous material where it first 
appears at Cockleroy and Linlithgow Bridge, the lower Bo'ness coals might possibly 
be considered more nearly the equivalent of the lower Bathgate coals in point of time. 
Further, the lavas of the Bo'ness coalfield apparently form a group by themselves 
entirely distinct from the volanic zones of the Bathgate Hills to the south. It is highly 
probable, as Mr Cavett has suggested, that the conditions of sedimentation were entirely 
different on either side of a volcanic orifice somewhere in the vicinity of Little Mill. 
It is unnecessary to describe in detail the stratigraphy of the Bo'ness coalfield. 
That has been admirably done already by Mr CapE 1, and the Little Mill district alone 
still remains more or less of a puzzle. Petrographically, the lavas of Bonnytoun Hill, 
south of the Roman road, can be readily subdivided into three zones—a lower zone of 
coarse-grained olivine-dolerites between the Red Coal and the Wandering Coal ; a middle 
zone of porphyritic olivine basalts between the Wandering Coal and the Western Main 
Coal ; and an upper zone of coarse-grained dolerites between the Western Main Coal and 
the Muirhouse coals. The middle zone alone can be traced below the ash of Little Mill 
to Pepper Hill and Linlithgow Bridge. To the north the lower zone can be traced 
continuously to the Bonhead fault, but the two upper zones, north of the Roman road, — 
apparently pass into finer-grained doleritic basalts, which persist throughout the 
remainder of the coalfield. The rock exposed above Bonsyde is similar to the lavas of 3 
the middle zone to the west, and is probably a displaced portion of the other lavas 
of the hill. | 
The Fifth Volcanic Zone, or The Kipps and Bishopbrae Lavas. 
This zone lies a short distance above the Index limestone, and may be traced, with 
interruptions, from Linlithgow to Bathgate. Between the Avon Paper Mills and the 
vicinity of Cockleroy, where this zone reaches its greatest thickness, the only ex- — 
posure is found in the Cauld Burn at East Belsyde. It is highly probable, however, 
that this zone is continuous throughout. Petrographically, the lavas belong mostly — 
to types of olivine-basalt, and limburgitic varieties may be studied with ease in the — 
neighbourhood of Kipps. Coarser-grained doleritic types occur here towards the — 
summit of the series, and appear also in the river Avon at Linlithgow. 
Above the lavas and below the Dykeneuk limestone evidence of the continuance of 7 
voleanic action is found in Carriber Glen, where a thick series of ashy sandstone and — 
voleanic mudstones, in places fossiliferous, are exposed in the gorge of the river Avon. — 
Similar ashy sandstones are found at Threegables, east of Bowden Hill; and in a 
streamlet between Lochcote and Gormyre a bed of ash occurs on approximately the — 
same horizon, overlaid by a peculiar blue mudstone, which in places much resembles a — 
decomposed igneous rock. 
