452 JOURNAL OF THE PLYMOUTH INSTITUTION. 
called by the miners — Greywacke. The local geologists of his 
day, however, applied that term specially to trappean and altered 
slaty rocks. 
To Professor Sedgwick and Sir E. Murchison we are indebted for 
that identification of the places of our chief Devonshire rocks 
which is now generally, though in somewhat modified forms, 
accepted. The bulk of the rocks of the centre of the county 
they classed as Carboniferous ; those bounding them north and 
south as of the Old Eed Sandstone period, for which they proposed 
the term Devonian. The idea that the latter rocks were Old Eed 
was not absolutely new. Mr. Prideaux spoke of the sandstones 
of Eovisand as having that character. Mr. Lonsdale, in 1837, 
suggested, on palseontological grounds, that the South Devon rocks 
would be found to occupy an intermediate place between the 
Carboniferous and Silurian systems. Sedgwick and Murchison 
were then engaged in their investigations in the district; and as 
the result in 1839 announced this as their conclusion. 
Though the identification of the rocks of North and South Devon 
as of Old Eed age is generally accepted, the acceptance is by no 
means universal. There is no question that these rocks are inter- 
mediate between the Silurian and the upper part of the Carbon- 
iferous systems, but there has been much question whether in truth 
they are really Devonian or Old Eed Sandstone at all, and whether 
they are not lower members of the Carboniferous formation. 
I shall not venture into this controversy, but only indicate its 
leading features. 
The first to assail in any formal and set form the conclusions 
of Sedgwick and Murchison was the late Mr. Jukes, who held 
that while there were undoubtedly rocks in North Devon of Old 
Eed age, most of those so classed were Lower Carboniferous. This 
interpretation he based on his intimate knowledge of the geology 
of the South of Ireland. Subsequently Mr. Jukes advocated the 
opinion in its complete form, that the Devonian slates and lime- 
stones which contain marine fossils (and in these our Plymouth 
rocks are included) are superior to the Old Eed Sandstone. 
Mr. Jukes expounded his hypothesis in full detail before the 
Geological Society of London in 1866 ; dealing then with the rocks 
of North Devon. In 1868 he read a paper before the Geological 
Society of Ireland, in which he set forth the results of his 
examination of the rocks of South Devon and East Cornwall. 
