82 REPORT— 1874. 
no doubt, was commenced somewhere about this period. Eventually the depression 
increasing towards the centre of the faults crossing the lake, caused a lateral 
upheaval on each side, giving the finishing touch to the basin depression and 
causing an inflow from all sides. The outflow may now possibly have begun to 
take its way along the great valley of depression which it still occupies. In the 
course of time large rivers carried down immense quantities of detritus into the 
water-filled hollow, and spread it into a great lake-delta, silting up the greater 
part of the lake. Finally, it is possible that some depression of the country to the 
north ensued, draining the lake to some extent; for near Belfast a clay-deposit 
containing Nucula oblonga, &c. has been found about 120 feet above the sea, which 
is referred to Newer Pliocene age. It is unnecessary to trace the history of the 
Lough past this point, because the physical geology has remained essentially the 
same to the present day. 
The basin could not have been of prebasaltic age, because the Chalk is every- 
where of nearly uniform thickness, and must have formed a flat surface, probably a 
plain of marine denudation, when the basalt was deposited on it, both together being 
afterwards upheayved around the edges. Moreover, all the most important faults in 
the district being of postbasaltic age (in part at least), the previous features of the 
country ae have been quite distinct from the appearance they afterwards 
resented. 
‘ Details of the probable mode of Formation of the Lough.—The author proceeded to 
describe the faults which crossed the Lough, premising that they left little or no 
trace, either in the shape of the ground or of the lake margin; all that he 
stipulated for being that they were the means of determining the flow of water 
into, and the removal of detritus out of, the centre in the first instance. 
The principal fault is that forming the north-west boundary of the Dungannon 
coal-field (where it has a throw of at least 2000 feet) running N.W., no doubt 
crossing the lake, and most probably joining the great Templepatrick fault, which 
has a downthrow of some hundreds of feet to the same side (the south). It appears 
to die out at either extremity. 
North of the last, the southern boundary fault of the Annaghone coal-field has 
been traced nearly parallel to it, with a downthrow also to south, proved in a trial 
for coal to be at least 300 feet, but considered to be much more. 
Further north are two large faults running towards the Lough, by Coagh; and 
these throwing towards each other would form a trough, the direction of which 
would coincide with the deep part of the lake. 
Further on towards Slieve Gallion, and in the country around it, are numerous 
faults, which have a considerable share in modifying the shape of the country. 
On the east side besides the Templepatrick fault there are several which can be 
observed in the high grounds about the valley of the Lagan, and whose general 
downthrow is rather towards the Lough. 
All the above are either partially or entirely in age postbasaltic. A large post- 
triassic fault has been observed near Dungannon, which if continued, and that it 
is also postbasaltic, would pass south of the lake and upheave the ground in the 
same direction. ~ 
The effect of all these faults would be, therefore, to cause a great depression of the 
ground now occupied by Lough Neagh; but before the final completion of that 
basin, the valley of the Lagan was denuded. ; 
The author concluded with evidence as to the enormous amount of denudation 
which took place over the basaltic district during the latter part of the Miocene 
period, and suggested that a great part, if not the whole, of Ireland may have also 
es at the same time, finally summarizing the chief points dwelt on as 
ollows. 
Recapitulation.—(1) The Lough is of an age intermediate between the Lower 
Miocene and the Glacial periods. (2) It is not a true rock-basin, and could not 
have been formed by ice-action either of Miocene or subsequent age, but is part of 
an area of depression, and is due to the existence of one or more series of faults, 
assisted by subaerial denudation. (3) That the extensive deposit of clays and 
sands, &c. found on the southern shore and for some miles inland is the delta of a 
former large river, which flowed very much in the same course that either the 
