222 Reports and Proceedings : 
several widely disseminated metals, the presence of which in mineral 
waters has only of late been discovered by the spectroscope, having 
real therapeutic value. 
The infilling of fissures with mineral matter by hot springs was 
next touched on; and it was suggested that metallic substances may 
possibly be given off by the highly heated waters at profound depths, 
there forming the metalliferous portions of lodes, which, in course of 
time, when lifted upwards with the enclosing rock-masses, and 
exposed by denudation, come within the miner’s reach. 
The metamorphism of sedimentary rocks, on which the study of 
thermal waters has thrown some light, was the subject which next 
engaged attention. Metamorphic rocks are largely composed of 
minerals that are now regarded as having been derived from liquid 
solutions of far less temperature than that of the state of igneous 
fusion from which they were once supposed to have crystallized. 
Thermal waters are known to be ‘ powerful causes of decomposition 
and chemical reaction in rocks through which they percolate ;’ and 
their partial interference with strata at different horizons (the pos- 
sibility of which Sir Charles illustrated by reference to the obstructed 
hot spring in the Wheal-Clifford lode) was alluded to as a probable 
cause of alternate altered and unaltered rock-masses. Sir C. Lyell 
mentioned Sénarmont, Daubrée, Delesse, Scheerer, Sorby, Sterry 
Hunt, G. Rose, and Bunsen as investigators of the effects of hydro- 
thermal agencies; and he warned geologists not to be too ready to 
impugn ‘the Huttonian doctrine as to the intensity of heat which 
the production of the unstratified rocks, those of the plutonic class 
especially, implies.’ In a few words, the shifting of volcanic areas, 
thought by some to be a proof of the general distribution of internal 
heat, was then doubtfully associated with the local chemical changes 
with which mineral waters are concerned. 
Referring to the comparatively modern date at which he had in-. 
timated that the Bath Waters may have sprung forth, Sir C. Lyell 
explained that ‘mighty changes’ had come over the western part of 
Britain even within the period during which the existing species of 
Testacea had inhabited the British seas, lakes, and rivers. Of Sir 
R. Murchison’s ‘ Malvern Straits,’ hypothetically spoken of by him 
a quarter of a century ago, actual proofs had lately been seen in 
marine shells of recent species found in Drift on that area, 
deposited when the site of Bath was water-covered at the foot of 
islands which are now the Cotswold Hills. The uprising of land 
that gave the present relation of sea and land was not so striking as 
that manifested, for the same period, by upraised marine shells on 
the top of Moel Tryfaen, on the flanks of Snowdon; where Mr. 
Trimmer, in 1831, found fossil Arctic shells, of existing species, at 1360 
feet above the present sea-level. Lately this interesting bed has 
been again exposed. Sir Charles, who has seen this deposit lately, 
with Mr. Darbyshire and the Rey. W. Symonds, said that ‘a con- 
siderable portion of what is called the Glacial. Epoch had already 
elapsed before the shelly strata in question were deposited on Moel 
Tryfaen, as we may infer from the polished and striated surfaces of 
