234 Reports and Proceedings — 
F E.S.E., F.G.S., Professor of Natural History in the University of 
St. Andrews. 
The object of this paper was the investigation of the strata 
between the great volcanic seines of the Lake-district, the Borrow- 
dale rocks, and the sedimentary rocks called Coniston Flags by 
Prof. Sedgwick. The Borrowdale series, the Green Slates and 
Porphyries of Sedgwick, are underlain by the Skiddaw Slates, 
forming the base of the Silurian series, and equi valent in age to the 
Arenig rocks of Wales, according to their fossil coutents. The 
Borrowdale rocks consist of ashes and breccias, alternating with 
ancient lavas, and are partly subaerial, partly submarine. They 
contain no fossils except in a band of calcareous ashes near the 
summit of the group, which is followed by the Conistone Limestone, 
with or without the Intervention of a bed of trap. The fossils are 
of Bala types. Sometimes this band is recognizable, with no traces 
of fossils except cavities filled with peroxide of iron. The authors 
regard this as proving the prevalence of volcanic activity in the 
Lake District up to the later portion of the Bala period. 
The deposits specially discussed in the paper sent, lie, apparently 
quite conformably, upon the Borrowdale rocks, and are grouped by 
the authors as follows, in ascending Order : — 
1. Dufton Shales. 
2. Coniston Limestones and Shales. 
3. Graptolitic Mudstoues or Skelgill Beds. 
4. Knock Beds. 
The “ Dufton Shales ” are a well-marked, but locally distributed 
group of muddy deposits, especially well developed in the Silurian 
area uuderlying the Cross Fell ränge, where they are seen in four 
principal exposures, and their tliickness probably exceeds 300 feet. 
They are richly fossiliferous, the fossils being general ly of Bala 
types ; and they may be regarded as forming, palaeontologically, the 
base of the Coniston Limestone. The fossils sometimes occur in 
ash-beds ; and the continuance of these conditions leads the authors 
to believe that there was no break between these shales and the 
uuderlying Borrowdale rocks. 
The “ Coniston Limestone ” has long been recognized as the best- 
defined division of the Lower Silurian rocks of the north of England. 
Its ränge and characters, and those of the associated shales in 
different localities. are indicated by the authors ; and from the con- 
tained fossils, they refer it, at least approximately, to the horizon of 
the Welsh Bala Limestone, wliilst they regard it as the precise equi- 
valent of the Lower Silurian of Portraine (co. Dublin), and of that 
of the Chair of Kildare, both of which are of Bala age. 
The “Graptolitic Mudstones” overlie the Coniston Limestone, 
wherever the summit of the latter is to be seen. Besides Grapto- 
lites, they contain many other fossils, including Corals, Brachiopods, 
Cephalopods, and Crustaceans; and from the consideration of the 
whole fauna, the authors are led to believe that the position of these 
deposits must correspond either with the highest beds of the Bala 
series, or with the lower portion of the Llandovery group. In their 
