THE BRITISH SCIENCE ASSOCIATION. 323 
tory began as now written in the rocks, all known formations were comparatively 
so recent in geological time that there was no reason to believe that they were 
produced under physical circumstances differing either in kind or degree from 
those with which we were now more or less familiar. All, or nearly all stratified 
formations had been in asense metamorphosed, excepting certain limestone: the 
fact of loose, incoherent sediments having been by pressure and other agencies 
turned into solid rocks, constituted a kind of metamorphism. Common stratified 
rocks chiefly consist of marls, shales, slates, sandstones, conglomerates and lime- 
stones, generally distinct and definite; but not unfrequently a stratum or strata 
might partake of the characters in varied proportions of two or more of the above 
named species. 
He would not discuss the theory of the causes which produced the metamor- 
phism of stratified rocks; but he might say that under the influence of deep un- 
derground heat, aided by moisture, sandstones had been converted into quartzites, 
limestones had become crystalline, and in shaly, slaty and schistose rocks under 
like circumstances there was little or no development of new material, but rather 
in the main a rearrangement of constituencies according to their chemical affini- 
ties in rudely crystalline layers, which had been very often more or less devel- 
oped in pre-existing planes of bedding. In Cornwall, Devonshire and Ireland it 
was now well known that metamorphic rocks were common, and the cases of 
metamorphism of Silurian rocks on the Continent could be easily multiplied. The 
same kind of phenomena were common in Canada, the United States and India. 
Turning to the Devonian and old red sandstone strata of England and Scotland, 
he found that metamorphic action had also been at work, but in a much smaller 
degree. ‘These rocks were of the same geological age, though they were depos- 
ited under different conditions, the first being of marine and the latter of fresh- 
water origin. With regard to the carboniferous strata, he knew of no case 
where there had been a thorough metamorphism in Britain except that in South 
Wales, beds of coal in the west of Carmarthenshire and in South Pembrokeshire 
gradually passed from so-called bituminous coal into anthracite. He knew of no 
other strata that had suffered from metamorphic action, and he had never seen or 
heard of metamorphic rocks of later date than those that belonged to the Eocene 
series. 
Enough, however had been said to prove that from the Laurentian epoch 
onward, the phenomenon of extreme metamorphism of strata had been of fre- 
quent recurrence, and extended partly to the Eocene series, equivalent to the 
soft, unaltered strata of the formations of the London and Paris basins, which, 
excepting for their fossil contents and sometimes highly inclined positions, looked 
as if they had only been recently deposited. Referring to the subject of volca- 
noes, the President said that the oldest volcanic products he knew of were of low- 
er Silurian age, and they were to be found in Wales and other parts of England, 
but he knew of no true volcanic rock in the Upper Silurian series. In the Old 
Red Sandstone of Scotland lavas and volcanic ashes were of frequent occurrence, 
