Papers read at the British Association at Montreal. 469 



out Drift, from which the following important points will be at 

 once seen : — 



1. Large tracts, shown as Chalk on one version, really consist, at 

 the surface, of the generally impervious Bouldei'-clay, whilst over 

 others the Chalk is covered by Brickearth and Clay-with-flints ; all 

 these beds being such as give an aspect to the country very different 

 from what we find where the Chalk is bare. 



2. Parts of the wide-spreading area of the London Clay (of the 

 Driftless maps) are really quite altered and deprived of their clayey 

 character, by the sheets, long strips, and more isolated patches of 

 gravel and sand that occur so often, whether along the river-valleys 

 or over the higher plains. 



3. The sandy permeable Crags are in great part hidden by Drift, 

 which, though often consisting of sand and gravel, is sometimes of 

 Boulder-clay. Indeed, so widespread is the Glacial Drift in the 

 greater part of Norfolk and Suffolk that only a Drift edition of 

 the Geological Survey Maps of the eastern parts of those counties 

 has been issued ; a map without Drift would necessarily be a work 

 of fiction. 



To illustrate the important bearing which these Drift maps have 

 on a great question, that of water-supply from the Chalk, the author 

 also exhibits some special maps, which he has made to show the areas 

 over which rain-water has access to the Chalk, as distinguished from 

 those over which the surface-water cannot sink down into the Chalk, 

 or can only do so very partially. These maps will be more 

 particularly noticed in Section G. 



4. — On the more Ancient Land Flokas of the Old and 

 New Worlds. 



By Sir "William Dawsox, K.C.M.G., LL.D., F.R.S. 



IN the Laurentian period vegetable life is probably indicated, on 

 both sides of the Atlantic, by the deposits of graphite found in 

 certain horizons. There is good evidence of the existence of land at 

 the time when these graphitic beds were deposited, but no direct 

 evidence as yet of land plants. The carbon of these beds might 

 have been wholly from sub-aquatic vegetation ; but there is no 

 certainty that it may not have been in part of terrestrial origin, 

 and there are perhaps some chemical arguments in favour of this. 

 The solution of the question depends on the possible discovery of 

 unaltered Laurentian sediments. 



The Silurian land flora, so far as known, is meagre. The fact 

 that Eopteris has been found to be merely a film of pyrite deprives 

 us of the ferns. There remain some verticillately-leaved plants 

 allied to Annularia, the humble Acrogens of the genus Psilophyion, 

 and the somewhat enigmatical plants of the genera Pachjtheca, 

 Prototaxites, and Berwynia, with some uncertain Lycopods. We have 

 thus at least forerunners of the families of the Asierophyllitece, the 

 Lycopodiacece, and the Coniferce. 



The comparison of the rich Devonian or Eriau flora of the two 



