Anniversary Address to the Royal Geological Society. 489 
Britain and Ireland the Lower Old Red Sandstone* occupies 
distinet basins in which “come local and often peculiar features, 
whereby even contiguous tracts are distinguished from each 
other. It is still possible roughly to make out, with more or less 
clearness, the limits of these basins, which seem sometimes to 
have been connected by narrows or shallows, and doubtless by 
occasionally closed water channels; in other cases to have been 
completely isolated.” Prior to Geikie’s researches it was gene- 
rally believed that the entire Old Red Sandstone of Scotland 
represented three distinct groups, but he believes that his work 
in the centre and south of Scotland proves the Old Red Sand- 
stone (Carboniferous and Silurian) to consist of only two divi- 
sions ; the upper portion passing conformably upwards into the 
Carboniferous formation, while the rocks formerly supposed to 
form two groups (Middle and Lower Old Red Sandstone) pass 
conformably downwards into the Silurians. He seems also to 
believe, that although the lower rocks in the different areas vary 
both lithologically and paleontologically, yet, chronologically 
they correspond, all having been deposited at the same time, 
but in different seas and under different circumstances. 
In England the Silurian rocks present somewhat similar as- 
pects, in some places partaking of the characters of the “ Upper 
Silurian,” and in others of the “ Lower Old Red Sandstone.” In 
South-west England, as in South-west Ireland, rocks of. Car- 
boniferous and Silurian types are intermingled. These have not 
been as yet satisfactorily worked out ; but as Geikie, Woodward, 
and other eminent petrologists, following in the steps of Jukes, 
are engaged in the investigation of them, we may expect that, 
before long, their proper chronological position will be estab- 
lished. 
In Ireland, although the fossil characters of the Scottish 
“ Lower Old Red Sandstone ” do not appear, yet we there obtain 
important and instructive facts. There are in this country two 
areas of deposition occupied by these rocks. The most northern 
is the western continuation of the rocks found in the central 
* T am not aware that Dr. Geikie ignores the Old Red Sandstone as a formation, as 
this does not appear in his paper. Whether he will eventually do so or not has still to 
be seen; he, however, distinctly states that in Scotland the ‘‘ Lower Old Red Sandstone” 
is conformable to the underlying Silurian strata, 
