io8 



HARDWICKK S SCIENCE-GOSSIP. 



It is known to lay on the islands in Loch Lundi and 

 Loch Nan Criche. The pair at Loch Lundi, however, 

 have been conjectured to be great northern divers, 

 but as they are very shy birds, it is almost impossible 

 to obtain a good look at them. The eggs found 

 there were certainly much larger than those of a 

 black-throated diver. Red-throated divers are much 

 more plentiful ; their nearest nesting-places are Loch 

 Tarff and Loch Knockie. One was shot not long 

 ago by one of our boys, a short distance from the 

 entrance of the Caledonian Canal. Cormorants are 

 in fair quantities ; nearly every day one or two can be 

 seen flying overhead to their feeding-grounds. A pair 

 is supposed to build on the shores of Loch Ness, but 

 no one has yet found the nest. Six kinds of ducks 

 either breed or visit us during the summer, namely, 

 the mallard, widgeon, golden-eye, tufted duck, shield- 

 rake, and teal. Mallards are very plentiful ; I have 

 seen upwards of three hundred rise together in some 

 of the bays down the lake. The tufted duck, widgeon, 

 and shieldrake are rare, and only seen occasionally. 

 A few pairs of golden-eyes inhabit the lakes, and the 

 teal is nearly as common as the mallard. The grey- 

 lag goose is occasionally encountered, and is supposed 

 to build at Loch Nan Ean, near Invermoriston. 

 Gulls of all kinds build on any of the lakes possessing 

 islands. The common gull is the most plentiful, and 

 lays on Lochs Tarff, Lundi and Nan Criche. Black- 

 headed gulls, on the other hand, are restricted to 

 Loch Lundi, where they keep a little corner to them- 

 selves. A pair of lesser black-backed gulls breed on 

 Loch Nan Criche. Kitiwakes, greater black-backed 

 gulls, and herring gulls are often seen, [but they, 

 however, prefer the west coast to lay their eggs. 



The above enumeration, which is by no means 

 exhaustive, will give some idea of the number and 

 variety of birds which frequent our neighbourhood. 

 The cause of this is, doubtless, to be found in the 

 diversified nature of the country, which is thus 

 admirably adapted to afford sustenance to our 

 feathered friends, and enable them to supply their 

 widely different needs. 



The Abbey School, Fort Augustus, N.B. 



THE GEOLOGICAL HISTORY OF THE 

 THAMES VALLEY. 



Abstract (by the author) of a Lecture delivered before 

 the Windsor and Eton Scientific Society, on 

 February 19th, 1891, by the Rev. A. Irving, 

 D.Sc, Senior Science Master in Wellington 

 College, Berks. 



Introductory Remarks. 



THE geological history of ' Father Thames ' has 

 a special and local interest for the millions of 

 dwellers upon his banks. But to the geological student 

 this interest is greatly magnified by the fact that of 

 the larger modern river-valleys of Britain that of the 



Thames (in its wider sense) is certainly one of the 

 most ancient. Its history from the geologic stand- 

 point is almost co-extensive with Tertiary time and 

 all that has followed since. We shall see, as we 

 proceed, that the Upper or Oxford Basin is a com- 

 paratively recent addition to the line of the Thames 

 drainage ; the true geological history of the Thames 

 is identified with the line of drainage marked 

 approximately by the valley of the Kennet, and that 

 of the Lower Thames (below Reading).* This must 

 be regarded as the lower course (Unterlauf) of 

 a great river whose middle course (Mittellauf) and 

 head-waters (Sammelgebiet) were found in the great 

 mountain-system which made the mountains of 

 Scandinavia continuous with the once higher 

 mountains of Brittany, the worn-down stumps of 

 those appearing in the palaeozoic and archrean rocks, 

 of the more mountainous portions of the north and 

 west of Britain. [Reasons were given for considering 

 this a more likely gathering-ground of the head- 

 waters of the great Eocene river, than a hypothetical 

 vast stretch of continental land to the west.] 



The duplicate basin of the modern Thames consists 

 of the Oxford Basin, draining chiefly Jurassic rocks ; 

 and the Lower or London Basin, in which we have 

 only to do with the rocks of Cretaceous and Tertiary 

 age, and with Quaternary and recent deposits. This, 

 latter basin, briefly sketched, lies in a synclinal valley 

 of the Chalk, the chalk hills rising to 975 feet at 

 Inkpen, the culminating point of the Kingsclere axis,, 

 and to 850 feet in the Downs of the White Horse range,, 

 no important transverse incision being made by rivers. 

 The Kennet rises near the Chalk escarpment to the 

 west at not more than 500 feet ; the valley of this- 

 river being probably the truncated valley of the chief 

 arterial line of drainage of Southern Eocene England. 

 As the Chalk escarpment is cut through on the north- 

 west, at the Pangbourne and Goring gorge, so the 

 Chalk escarpment of the North Downs is cut through, 

 by tributary streams, which rise on or near the axis 

 of the Weald. We pass by the question of the 

 relative claims of the * Seven Wells' or the ' Head of 

 Isis ' to represent the true source of the Thames,t not 

 only because the Windrush or the Cherwell may, for 

 length and volume of water, establish a better claim 

 than any of the streams which rise near the escarp- 

 ment of the Cotswolds above Cricklade, but much 

 more because, from the point of view of geological 

 histor}', no part of the present drainage of the Oxford 

 Basin has any claim whatever. The Kennet-Thames 

 line of drainage served as the channel of a much 

 greater volume of- water than in recent times, while 

 the present area of the Oxford Basin was drained in 

 other directions, mainly perhaps in the direction of 

 the Ouse, towards the old North Sea. 



The succession of the British rocks, the classifica- 



* See "Journal of the Geol. See," vol. xliv., pp. 178, 179. 

 i" See Professor Phillips, " Geology of Oxford and the Valley 

 of the Thames," chap. iii. 



