On the Geology of the Rio- Tinto Mines. 927 
The author concludes, therefore, that the “ Brown-clay series” 
is of much newer date than the “ Blue and grey series.” 
In conclusion, the author summed up the inferences drawn in the 
paper, correlated the Basement Clay of Holderness with the Chalky 
Clay of Lincolnshire, and suggested that the Purple Clay may be 
confined to the east side of the wolds. The classification he would 
propose .is therefore as follows :— 
Lincolnshire. Yorkshire. 
Hessle clay. Hessle and upper red clay 
Newer Glacial. of coast. 
Purple clay. Purple clay. 
Older Glacial = Chalky clay. Basement clay. 
2. “On the Geology of the Rio-Tinto Mines, with some general 
Remarks on the Pyritic Region of the Sierra Morena.” By J. H. 
Collins, Esq., F'.G.S. 
After briefly describing the geographical position of the Rio-Tinto 
mines and the occurrence at the same of pyritous ores amongst 
slates and schists which abut against eneissose rocks to the north, 
and pass under Tertiary beds to the southward, the author pro- 
ceeded to consider the general characters and associations of the 
pyrites-deposits, and then gave a general account of the Rio-Tinto 
district. The slates were described, and the fossil evidence recapi- 
tulated upon which an Upper Devonian age had been assigned to 
them. Analyses were furnished to show the changes due to 
weathering and to infiltration. The various intrusive rocks (syenite, 
diabase, and porphyries) occurring in the schists were described, 
and analyses of them given. The sedimentary iron-ores and their 
composition were next noticed, and the author ascribed their 
formation to deposition in lakes. 
The masses of pyrites which furnish the principal ores of Rio 
Tinto were then described, their mode of occurrence in fissures be- 
tween dissimilar rocks explained, and their formation discussed. 
The different kinds of ore obtained from the mines were noticed in 
detail, and several analyses added, giving samples both of the mixed 
ores and of the pure minerals. . 
The manganese-lodes were next described, and shown to be 
parallel to the pyrites-fissures, and frequently to be only branches 
of the latter. 
A summary of the author’s conclusions as to the stratigraphy of 
the district, the ore-deposits, and tue surface-geology was appended. 
3. “On some new or imperfectly known Madreporaria from the 
Great Oolite of the Counties of Oxford, Gloucester, and Somerset.” 
By R. F. Tomes, Esq., F.G.S. 
