30 
Lower Lias (averaging a thickness of 600 feet) : — 600 
Marlstone, or Middle Lias . . . . 200 
Upper Lias . . . . . . 300 
Inferior Oolite .. .. .. 230 
Fullers Earth .. ... .. 130 
Great Oolite .. .. .. 130 
Cornbrash .. .. . . 80 
Oxford Clay . . . . . . 600 
Coral Rag .. .. .. 180 
Kimmeridge Clay . . . . 600 
Portland Beds .. .. .. 170 
PurbeckBeds .. .. .. 150 
Making a total of . . . . 3370 feet 
The term Oolite is, as you are aware, formed from two Greek words, signifying 
egg-stone, because the stone resembles the roe of a fish in its structure. The 
true Oolite differs very distinctly from all the Liassic deposits, both lithologically 
and paleeontologically. The Lias rocks are those of quietly deposited mud and 
tranquil water, while the Oolites were evidently deposited under the influence of 
strong currents and strong sea waves. 
This singular Oolitic structure may be now seen forming at the dock gates at 
Birkenhead. Each little grain contains as a nucleus a bit of sand or shell. The 
Oolitic limestones of the Carboniferous rocks most generally contain a Gasteropod 
or Foraminifer, but in the Oolitic rocks I have not yet succeeded in finding more 
than a minute particle of sand or mud. 
The beds from the Inferior Oolite differ greatly from those of the Great 
Oolite in possessing a large proportion of peroxide of iron. In some instances 
very rich beds occur, affording rich ore well adapted for smelting and gas purify- 
ing. As a rule the Oolitic beds dip to the S E. In lithological structure they 
vary greatly, from the small white grains of the Great Oolite, to the large pea- x 
pellets of the Pisolitic beds at the base of the Cheltenham series. Now and then 
the beds are separated by marls. At one point a bed of marls occurs 7 feet thick, 
and well marked by Terebratula fimbria. 
Like the beds of the Lias, the Oolite has been stratigraphically arranged by 
means of the fossils, especially the Ammonites. This was first pointed out by 
Quenstedt, and brought into use in this country by Dr. Wright, of Cheltenham, 
who has divided the Cotteswold Hills into zones, viz., Jurensis, Murchisoni, 
Humphriesianus zones. 
We must therefore regard our Dundry Hill top in relation to them. And a 
most instructive ground it is for the Bristol geologist. It is full of beautiful fossils. 
Indeed, it contains more species than any other rocks of the same extent in the 
West of England. Our neighbourhood, too, gives some good examples of faults 
in the Jurassic beds. For instance, a very good one occurs near Paul ton, where 
the Inferior Oolite beds are thrown down 20 feet to the north, according to Mr. 
Conybeare. The life which existed during the Oolitic age was very different from 
that which existed before, and very greatly resembles that of Australia at the 
present day, where we find living the Port Jackson shark, the only remaining 
