214 PRESIDENTS ADDRESS. 
rare British species. Several scarce species of Carex occur, 
especially Carex irrigua, which was first noticed as a Bri- 
tish Plant by Mr. John Thompson, then of Crowhall Mill; and 
who has added many species observed in the neighbourhood al- 
luded to, to the Northumberland Flora. Amongst them may be 
enumerated Mieracium prenanthoides and Crepis succiscefolia. 
Allium schenoprasum was found in full blow, in which state it 
does not often occur, Geraniwm columbinum, was abundant on 
the Walltown Crag, and in a pond to the south-east of it, Vym- 
phea alba, and Nuphar lutea, were flowering in great profusion, 
and Ranunculus lingua grew at a short distance from its edge. 
The day was remarkaby fine, and the party, after a pleasant, 
though long wander, reached Haltwhistle just in time for a hasty 
dinner, and to return home by the last train from Carlisle. 
The Fourth Meeting was held, August 12, at Prestwick Car, 
near Ponteland, a space of flat, marshy and boggy land, about 
two miles across, with a considerable pool of rather shallow 
water communicating with the little river Pont by a deep ditch 
of about one-third water and the remaining two-thirds of filthy 
mud. It is difficult to account for this flat expanse of bog, 
marsh, and water. That it has once been more elevated is evi- 
dent, as the stumps of trees blackened, as is usual in bog wood, 
are scattered over its whole surface. When the lake is low, they 
may be seen in considerable numbers just showing themselves 
above the water. Two kinds of trees may be distinguished ; a 
species of fir, probably the Common Scotch Fir, as the wood, 
when sliced and put under the microscope, sppears to belong to 
that plant. The other tree is the Common Birch ; in this the 
bark in many cases is almost quite sound, whilst the wood is 
soft or altogether gone: thus furnishing us with the means of 
accounting for the fact, that in most of the larger fossil plants of 
our coal mines, we have the impression of the bark only, the 
place of the wood being usually occupied by mud or sand. How 
the trees at Prestwick Car have got into their present situation 
it is difficult to say : the appearance of the place, an extensive 
flat, like the bottom of a large dish, rising ground on nearly every 
sides forming the edge, would suggest the idea of subsidence of the 
