Anniversary Address to the Royal Geological Society. 199 
Small details are omitted in this map. The leading boundary 
lines are already nearly the same asnow. The Primary rocks are 
the mica slate, &c., of Donegal, the Ox Mountains, West Mayo and 
Achill, Croagh Patrick, and the stretch of country reaching from 
Lough Corrib to the north side of Clifden. The Transition divi- 
sion is Cambrian and Silurian; that of Wicklow, which is Older 
Transition, includes both. This, however, is still only conjecture. 
The Greywacke Slates, as he calls them, of South Cork are Older 
Transition. This erratum was to be almost immediately after- 
wards corrected. Indeed he had already made what we may call 
a step towards the truth, for the limestone of the Lee, Bride, Black- 
water, &c., valleys, which was supposed to be interstratified with 
the slates, and to be therefore Transition limestone, he declares 
to be Carboniferous, notwithstanding its questionable position. 
What we now call the Dingle Beds and Glengariff Grits are Newer 
Transition—that is to say, he had already assigned them the posi- 
tion which further investigation more strongly convinced him 
was the right one for these somewnat obscure rocks. But the 
Transition colour still extended over what he very soon found to 
be the Old Red Sandstone area of Middle and East Cork, the 
Galtee Mountains, Waterford, and Kilkenny. He had made, how- 
ever, a step inthe right direction by colouring this as Newer Transi- 
tion, whereas before it was simply Transition. But, on the other 
hand, he now carried the Newer Transition colour over the Com- 
meragh and Knockmealdown Mountains; a step in the wrong 
direction, which was, however, to be almost immediately retraced. 
The Secondary division extends from the Old Red Sandstone to 
the Chalk, both inclusive. Some of his Old Red Sandstone, such 
as that of Slieve Bloom, the Curlew Mountains, &c., he now made 
Yellow Sandstone ; which was with him a greater change than it 
would have been with others, since he was transferring the rocks 
in question from the Old Red to the Carboniferous. 
His division of the Carboniferous System was now nearly com- 
plete. It was as follows in ascending order :—Yellow Sandstone,* 
Lower, Middle or Calp, and Upper Limestone, Millstone Grit, and 
Coal Measures. But one member remained to be added ; which 
-* Jukes agreed with Griffith that the Yellow Sandstone of the N. of Ireland formed 
the base of the Carb. System, but considered that that of the S. is more probably lower. 
Griffith, however, adhered to his opinion while aware of Jukes doubts. 
