lvii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 
tombed in the general mass of geological accumulations ; on the con- 
trary, always bearing it fully in mind, we are convinced, with Mr. 
Sharpe, of the necessity of comparmg the older accumulations of 
North America and of Europe in great masses, and even to regard 
the groups pointed out rather as affording us the convenient means of 
comparison than as positively representing, to their boundaries, the 
divisions which the study of European geology may at present make 
it desirable to adopt. 
While Mr. Sharpe’s paper refers to the comparison of deposits so 
wide apart as North America and Europe, now separated by an 
ocean, a portion of which may or may not have existed between them 
in that olden geological time, a communication from Prof. Sedgwick, 
made to the Society at its last meeting, on the organic remains 
found in the Skiddaw slate, with some remarks on the classification 
of the older rocks of Cumberland and Westmoreland, brings us to a 
consideration of the divisions and subdivisions which can be effected 
in the accumulations of this early date, as they are found in the 
British Islands. Professor Sedgwick divides the Cumbrian and 
Westmoreland rocks into eight groups, above the granite, namely,—1, 
the Skiddaw slates, commonly dark-coloured, the lower part altered — 
by the granite; 2, a great group composed of a mass of trappean 
rocks, indefinitely alternating with quartzose, and more or less chlo- 
ritic roofing-slates, generally of a green colour, the igneous matters, 
whether erupted or recomposed, being contemporaneous with the 
ordinary sedimentary accumulations with which they are associated ; 
3, a series of deposits, chiefly dark-coloured flagstones and slates, 
more or less caleareous, the lowest beds passing into a limestone 
(Coniston limestone) ; 4, coarse and hard, light-coloured sandstones ; 
5, thin beds of sandstone, like the last, associated with large masses 
of roofing-slate and sandstone, in some places a thin band of impure 
concretionary limestone is found in the lowest part ; 6, a complicated 
deposit of sandstones, flagstones, &c., in the upper part of which are 
some greenish and reddish flagstones, appearmg, Professor Sedgwick 
thinks, to occupy the same place as the tilestones of the Silurian 
system in Wales and the adjoming parts of England. The seventh 
group is the old red sandstone, restmg unconformably upon the 
above, and upon this comes the eighth group, formed of the car- 
boniferous limestone, resting conformably upon the old red sand- 
stone, or overlapping its boundaries, and then resting unconformably 
upon the older groups. 
All these groups Professor Sedgwick points out are true physical 
groups, the results of certain changes or modifications of the physical 
conditions under which they were accumulated. And here the Pro- 
fessor insists upon physical groups being “‘the foundation of all 
geology, and out of all comparison the most remarkable monuments 
of the past physical history of our globe, so far as it is made out in 
any separate physical region.” ‘‘ Organic remains,’ he continues, 
“‘are, in the first instance, but accessories to the information con- 
veyed by good sections. But when the successive groups of organie 
remains are once established in coordination with actual sections, 
