9i 
THE GEOLOGIST. 
on the nature of calcareous deposits, and on the contemporaneity of certain 
groups of deposits, dependent on the oscillatory movements of land and 
sea, the author described his plan of showing on maps the relative thick- 
nesses of the two classes of strata under notice, by means of isodiametric 
or isometric lines (properly isopithic, or indicative of equal thickiie&s of the 
strata). 
Sandstone 
and 
Shah 
JSaJids-toTii 
and 
Shalo 
San cby Lm. csion t 
Sand yL imestone 
^andjj Limes tor 
Fig. 2.- 
-Distribution of the Calcareous and Sedimeatarj Strata of the Great 
Oohte, Oxfordshii-e. 
Mr. Hull then proceeded to show the application of the isodiametric 
system of lines to the Carboniferous strata of the midland counties and 
north of England ; showing that there is a south-easterly attenuation of 
the argillo-arenaceous strata, and a north-westerly attenuation of the cal- 
careous strata. The existence, in the Carboniferous Period, of a barrier 
of land crossing the British area, immediately to the north of lat. 52°, was 
insisted upon ; and, although this barrier was probably broken through (in 
South TVarwickshire) in the latter portion of that period, yet it divided, 
in the author's opinion, the coal-area into a north and a south portion, the 
latter showing a very different set of directions in the attenuation of its 
strata ; the shales and sandstones thinning out eastward and the lime- 
stones in the contrary direction. 
In conclusion, the author stated his opinion that the source of the 
Carboniferous sediments was in the ancient I^orth Atlantic Continent, for 
the existence of which Lyell, Godwin- Austen, and others have argued ; 
and he inferred that the shores of this Atlantis, composed principally of 
granitoid or metamorphic rocks, were washed on the west side by a current 
running south-west which drifted the sediment in that direction; and, on 
the other, by a current running south-east which carried sediment over 
the submerged British area. 
Geologists' Association. — February 3 — Professor Tennant, F.G.S., 
President, in the chair. The following papers were read : — 1. " On the 
Cretaceous Group in iS"orfolk." By C. B. Rose, Esq., F.G.S. The author, in 
an elaborate paper, described the general divisions of the chalk formation 
as exhibited in ]S^orfolk, and following the arrangement proposed by the late 
Mr. Woodward, he divided the beds into Upper Chalk, Medial Chalk, 
Hard Chalk, and Chalk Marl. The Upper and Medial Chalk he stated 
to comprise the chalk with flints (the upper division of other geologists), 
and the author considers this distinction legitimate, inasmuch as the 
uppermost bed at iSTorwich contains organic forms which are not met with 
in the medial bed. The distinguishing characteristics of the several 
beds ^^ith their peculiar fossils^ and the local limits of each formation were 
fully described, and the paper w as illustrated by an elaborate section of 
the strata of the county. 
2. " On the Plasticity and Odour of Clay." By C. Toralinson, Esq. 
The author pointed out some of the most remarkable considei-ations in re- 
lation to this subject, such for instance as the fact that clay is only plastic 
up to a certain temperature ; when heated beyond that point (which the 
author believes, from experiments performed by hiin, to be somewhere be- 
