TRANSACTIONS OF THE SECTIONS. 73 
At a later stage the country was submerged beneath the waters of the Inter- 
pone sea, which deposited the sands and gravels which overlie the Lower 
oulder-clay ; and subsequent emergences during the stage of the Upper Boulder- 
clay, together with atmospheric agencies constantly at work whenever land has 
been exposed, have moulded the surface into the form we now behold. 
It will thus be seen that the physical geologist, whether a Vulcanist or a 
Neptunist, has in this region abundant materials on which to concentrate his 
attention. 
Voleanie Energy.—In connexion with this subject, it may not unnaturally be 
expected that I should make some allusion to the views of Mr. Robert Mallet on - 
“Volcanic Energy,” which he has recently unfolded in the ‘ Philosophical Trans- 
actions of the Royal Society’*. My limits, however, forbid more than a cursory 
glance at this subject. Stated in a few words, volcanic energy, according to Mr. 
Mallet, has its origin primarily in the contraction of the earth’s crust, due to secular 
cooling and the tendency of the interior molten matter to fall inwards and thus 
leave the exterior solid shell unsupported. The lateral pressure arising therefrom 
(which, as Mr. Mallet shows, is vastly greater than the vertical weight of the crust) 
is expended in crushing portions of the solid crust together, along lines of fracture 
which are supposed to correspond to those of the voleanic cones which are distri- 
buted over the earth’s surface. Each successive crush produces an earthquake- 
shock, and is converted into heat sufficient to melt the rocks which line the walls 
of the fissure or lie beneath at high temperatures, and which, in presence of elastic 
steam and gases, are erupted at intervals both of time and place. 
in the words of the author of these views :—“ The secular cooling of the globe 
is always going on, though in a very slowly descending ratio. Contraction is 
therefore constantly providing a store of energy to be expended in crushing parts 
of the crust, and through that providing for the volcanic heat. But the crushing 
itself does not take place with uniformity ; it necessarily acts per saltum after 
accumulated pressure has reached the necessary amount at a given point, where 
some of the unequally pressed mass gives way, and is succeeded perhaps by a 
time of repose or by the transfer of the crushing action elsewhere to some weaker 
point. 
It cannot be denied that Mr. Mallet’s theory seems to be consistent with many 
observed facts connected with volcanic action. It has for its foundation an incon- 
testable physical hypothesis, the secular cooling of the earth, and it seems to throw 
considerable light upon several observed phenomena of voleanic action—such as the 
distribution of cones and craters along great lines, the intermittent character of 
eruptions, and the connexion of earthquake-shocks with voleanic outbursts. There 
are some statements in Mr. Mallet’s paper which few physical geologists will be 
inclined to accept, such as the non-existence of true volcanoes before the Secon- 
dary or Mesozoic period. The Silurian volcanic districts of North Wales and of 
the west of Ireland, and the Carboniferous volcanic districts of Limerick and 
Scotland, bear witness against the soundness of such a view. ‘This statement, 
however, does not necessarily invalidate the general views of the author; and I 
cannot but think that the publication of Mr. Mallet’s paper has enabled us to take 
a very long stride in the direction of a true theory of volcanic energy. 
Further Researches on Eozoon Canadense. By W. B. Carrenter, 2.8, 
On the Fossils of the Posttertiary Deposits of Ireland. 
By the Rev. Joun Grater, D.D. 
At the last Belfast Meeting in 1852 the author gave a list of the shells found in 
the alluvial deposits of Belfast. To the ‘Natural-History Review,’ vol. vi., for 
‘i * 1873, vol. clxiii. p. 147. . 
1874. 6 
