INTRODUCTION. XXi 
The introduction of the May Hill sandstone as a part of the Wenlock group is the only 
important change I have made in the corresponding portion of the “Tabular View” which is 
prefixed to the “Second Fasciculus of the Cambridge Paleozoic Fossils.” It gives a true 
physical and paleontological base to the Silurian Series: and assuredly there is not (under 
this arrangement) any such thing in nature as a “Middle Silurian Group,” which inseparably 
links together the Cambrian and Silurian Series, and makes them into one System. The 
May Hill subgroup is not unfrequently discordant to the older groups, on which it rests; and 
its fossils unite it unequivocally to the Wenlock group. It must therefore, both on physical 
and paleontological evidence, be cut off from the shelly sandstone of Caer Caradoc and Horderly; 
to which it is discordant in position, and with which its paleeontological relations are not com- 
parably so near as to the Wenlock Group. It is in fact, as now given in the Table, an integral 
portion of the Wenlock group. 
Lower Paleozoic Division as developed in the Cumbrian mountains of the North 
f England. 
( A group of vast thickness, and probably admitting of several subdivisions. 
iia Gidddaw slate In some of its upper beds a few graptolites and fucoids have been found. 
(Lower Cumbrian) .. Generally it is without a trace ot fossils. Near the Granite of Skiddaw 
Forest entirely metamorphic. It is the supposed equivalent of the Long- 
mynd slate (1 a) of the Cambrian series. 
A group of enormous thickness, composed of alternating masses of slate, 
sandstone, porphyry. porphyritic conglomerate, trap-shale, &e. &e. It 
forms no passage into the Skiddaw slate, and is sometimes separated from 
it by trappean conglomerates. The conglomerates become attenuated, and 
2. Chloritic slate and por- pass into trap-shales (schaalstein) ; and the shales pass into roofing-slate. 
phyry The alternations are innumerable. The great deposits of slate are good 
(Middle Cumbrian) . mineral equivalents of the Llanberris and Festiniog slates. The group 
seems to pass, at one extremity, into the calcareous slates of the Coniston 
group ; and (when taken collectively) may be considered as the equivalent 
of all that part of the Cambrian series which extends from the Llanberris 
and Bangor slates to the Lower Bala rocks inclusive. 
3. Coniston group a. Coniston limestone and calcareous slate. 
(Upper Cumbrian) . (6. Flagstone; generally calcareous*. 
Equivalents of the Cambrian Series. 
pa 
* While the May Hill sandstone was confounded with the Caradoc group, and the Coniston limestone and flagstone 
were confounded with the Caradoc sandstone and Wenlock shale, the Coniston grits appeared to be quite anomalous 
among the true Silurian groups: but now that these grits have found their right place, the anomaly ceases altogether. 
They produce a remarkable impress on the physical features of the Silurian country of the North of England; and spite 
of their general sterility, they make a noble exhibition of the May Hill sandstone, and thus form the natural base of the 
Silurian series of the Cumbrian mountains. 
There neyer was any real difficulty in the natural succession of the physical groups of Cumberland and Westmore- 
land; and I could have described this succession, in 1824, as well as, perhaps better than, it is given in this Tabular 
View. The only subsequent difficulty was in attempting to put the successive groups into co-ordination with those of 
Wales and Siluria; and so long as the sections, the fossil lists, and the nomenclature of the “ Lower Silurian” rocks were 
