1852.] OF THE ROYAL INSTITUTION. 167 
and upper Eocene periods, but also to the absence in the pebble-beds 
constituting the base of the tertiary series of Auvergne, Cantal, and 
Velay of any pebbles of volcanic origin. 
The Lecturer concluded by stating that the formation of every 
mountain chain and every elevation and depression of land bears 
witness to internal changes at various depths in the earth’s crust. 
The alteration has consisted sometimes of the expansion, and 
sometimes of the contraction of rock, or of the semi-liquifaction 
or complete fusion of stony masses and their injection into rents of 
the fractured crust occasionally manifested by the escape of lava 
at the surface. Every permanent alteration therefore of level may 
be regarded as the outward sign of much greater internal revo- 
lutions taking place simultaneously far below. Even the precise nature 
of the changes in the texture of rocks produced by subterranean 
heat and other plutonic influences since the commencement of the 
Eocene period can be detected in a few spots especially in the 
central axis of the Alps where the disturbing agency had been 
intense. The table might be covered with specimens of gneiss, 
micaschist and quartz rock, once called primitive, and once supposed 
to be of a date anterior to the creation of living beings, which 
nevertheless were sedimentary strata of the Eocene period which 
assumed their crystalline form after the flints of Blackheath were 
rolled into shingle, and even after the shells of the London clay 
and the nummulites of the overlying Bagshot sands were in ex- 
istence. 
Yet however remote may be the antiquity of the Blackheath pebble- 
bed as demonstrated by the vast amount of subsequent change in 
physical geography, in the internal structure of the earth’s crust and 
in the revolutions in organic life since experienced, its origin is pro- 
bably as widely separated from the era of the Chalk as from our own 
times. For the fossils of the chalk differ as much from those of the 
oldest tertiary strata near London, as do the last from the organic 
beings of the present era. Nevertheless the white Chalk itself with 
its flints is considered by every geologist as the production of a 
modern era, when contrasted with the long series of antecedent rocks 
now known, each formed in succession when the globe was inhabited 
by peculiar assemblages of animals and plants long since extinct. 
[C. L.] 
In the Library were exhibited : — 
Fifty Pebbles from Blackheath and Woolwich, collected by the late 
Major Boys of Woolwich— Specimens of Gold Quartz, Sul- 
phuret of Mercury from California, and Topaz with Mica, &c. 
{Exhibited by Mr. Tennant ] 
Bronze Cast of Napoleon, taken shortly before death — Judge 
Fraser’s Lion-spear — Caffre Instruments of War. [Exhibited by 
Dr. W. V. Pettigrew, M.R.I. &c.]} 
Seaward’s Patent Brine-valve and Saline Detectors — and specimen 
