REPORTS. 
xxi 
complete insulation of the western peninsula at the time of 
its deposit, when the water flowed freely between the two 
channels through this strait. From the evidence thus obtained, 
this must have been the condition at the close of the Miocene, 
but more probably during the Pliocene period. With the exception 
of the Miocene lake deposits of Bovey Tracey, in Devon, 
Ardtun, in the Isle of Mull, and Giant's Causeway, this is the 
only known Tertiary deposit in any part of the British Islands, 
independent of the boulder drift, outside of the two districts 
known as the London and Hampshire Basins. But as the Miocene 
deposits are entirely lacustrine, it follows that the St. Erth bed is 
the only marine Tertiary deposit in the British Islands, beside 
those of the south-east of England, and as such it has a special 
bearing upon the physical geography of this south-western part 
of the island at the time, and is therefore, from a local point of 
view, very interesting and valuable. 
" 5. By the provision of another table-case a sufficient amount of 
accommodation has been secured for the due display of the 
natural increase of the past year, as well as to relieve the 
previously congested condition into which the cases had fallen. 
The Eeport of the Curator of Petrology was as follows : 
"The Curator of Petrology is glad to be able to report the 
collection in his charge to be at length in such order that he 
is enabled to give a synopsis of its principal contents, with the 
chief localities to which the specimens belong. The classification 
is somewhat dependent on the space ; but Cases II. to VII. 
contain local rocks ; Case VIII. rocks of the United Kingdom ; 
Cases IX. to XL foreign rocks. Case I. typical series. 
" Case I. Typical specimens ; with some special local rocks, the 
leading rock-forming minerals, and examples from Raised Beaches : 
" Typical series. — Granite, Dartmoor ; Shrift Granite, Hansdorf 
(Silesia); Pegmatite, South Africa; Protogine, Mount Blanc; 
Epidotic Granite, Dedham (U.S.A.); Syenitic Granite, Syene ; 
Syenite — Charnwood, Uddevella (Sweden), Portland (Maine) ; 
Augite Syenite, Monzoni (Tyrol); Elseolite Syenite — Laven 
(Norway), Litchfield (Maine); Glimmer Syenite, Vosges ; Aplite, 
Jersey ; Granulite, Rohrsdorf ; Greisen, Geyer (Saxony) ; Trowles- 
worthite, Trowlesworthy ; Luxulyanite, Luxulyan ; Diorite, 
Guernsey ; Orbicular Diorite (Napoleonite or Corsite), Corsica ; 
b 2 
