BONXEY : ox THE ORIGIX OF THE BRITISH TRIAS. 5 
angular fragments of more or less local rocks being mixed with 
})ebbles, characteristic of the latter formation ; similar pebbles, 
frequently of quartz, but sometimes of clay, and generally 
rather small, occurring occasionally in the sandstone itself. 
The Waterstones consist generally of alternating layers, 
usually not thick, of similar grejdsh sandstone and red marl, 
like that in the uppermost division. Its maximum thickness, 
so far as I can a,scertain, is about 300 feet, but it seldom exceeds 
half that amount and is often thinner, so that, as it is obviously 
a transitional formation, we may pass on to the Red Marl. This 
overlaps even the Lower Keuper sandstones, and maintains 
its lithological characteristics, as already mentioned, from the 
north-east of Ireland on the one hand and Yorkshire on the 
other to the extreme soutli on the Devon coast. Probably 
it extends beneath the sea to France, for the Keuper Marl in 
Normandy, where I saw it, closely resembled that of our owti 
country. This formation apparently attains its greatest tliick- 
ness in Cheshire, where Professor Hull makes it about 3,000 
feet ; in the central parts of Staffordshire it may be some 
1,500 feet, but in the neighbourhood of Coventry and Warwick 
this is reduced, according to Mr. Howell, to 600 feet. That 
is about its measurement in Gloucestershire and Xottingham- 
shire ; apparently it becomes thinner in the neighbourhood 
of the Bristol Channel, but thickens again towards the south, 
attaining from 1,000 to 1,350 feet on the shores of the Enghsh 
Channel. Where it abuts on older rocks, iatercalated breccias 
are not unfrequent, obviously formed near shores with a rising 
strand line ; of these the so-called Dolomitic Conglomerate 
in the Mendip region is a conspicuous example. The Keuper 
Marl, indeed the Trias as a whole, obviously tliins out in the 
neighbourhood of Northampton, for its total thickness in a boring 
near that towTi was just under 60 feet, while it was not found 
beneath the London and North Western railway station, or 
under Kingsthorpe, Kettering, or Orton. It has not been struck 
in any of the borings in the eastern counties from Suffolk to 
Kent. In saying this I do not forget the red rocks found 
beneath Kentish Town, Crossness, Richmond, and Streatham, 
but I am convinced that these are reaUy Palaeozoic. 
