Sept. 9, 1886] 
NATURE 
451 
beneath the London district. The clays of the Lias, Oxfordian, 
and Kimmeridgian probably indicate a direct discharge of sedi- 
ment into the sea,! the limestones, depression sufficing to convert 
valleys into fjords, in the upper parts of which sediment was 
deposited so that the waters of the sea were clear. The deposits 
of the Purbeck and Weald indicate that the western river still 
drained an extensive area, and a gradual rise of land in later 
Jurassic times, especially towards the south, appears to have 
advanced the river delta eastwards, and to have limited the area 
of the Jurassic sea on the north. 
Towards the end of the Neocomian, owing to a widespread 
subsidence, the sea once more returned to South-Eastern England, 
and a communication appears to have been opened between it 
and the Speeton basin. This comparatively narrow strait was a 
region of considerable denudation and of strong and shifting 
coast currents.2,> The Cretaceous subsidence at first brought 
back physical conditions not very different from those prevalent 
in Oxfordian and Kimmeridgian times, but later on a very 
considerable depression must have so far submerged the northern 
continental land as either to break up the parts adjacent to 
Britain into groups of islands, or at least to flood the valleys so 
completely as to prevent any discharge of sediment into the sea. 
The erratics of the Cambridge Greensand suggest that a free 
communication into the northern ocean was established, anterior 
to the formation of the Chalk marl, through some part of the 
present interval between Scotland and Scandinavia, so as to set 
up a coast current with a southerly drift of shore ice near the 
eastern part of England; to this also may be due the erosion of 
the Cambridgeshire Gault. 
The larger part of Britain was dry land during the Eocene, 
though the sea after retreating appears to have again encroached 
over the southern and eastern districts of England. The sands 
may indicate that the western river again resumed its course ; # 
the extension of the London Clay up our eastern coast suggests 
that the northern river still flowed. But with the important 
disturbances which closed the Eocene and ushered in the con- 
tinental conditions of the Miocene—new flexures along the old 
east and west lines—the earlier physical features appear to have 
been finally obliterated, and the sculpture of the English low- 
lands began. ‘The tale of the volcanic outbursts of Western 
Scotland has been so well told by my friend and predecessor 
Prof. Judd that I need do no more than recallit to your minds. 
The Pliocene deposits of Eastern England indicate a new 
encroachment of the Franco-Belgian Tertiary sea. 
Thus ends my sketch, too lengthy, I fear, for your patience, 
yet too brief to: allow of a complete treatment of the subject. 
. It may, however, ‘suffice to indicate that in geology the ‘task 
of the least” is by no means despicable, and that great results 
may be hoped from apparently small means; that in this 
search for “ Atlantis through the microscope” we may find it 
very near at hand, and may discover analogies, as has been 
indicated in our President’s address, between the two borders 
of the ocean which severs Europe from America. An enlarged 
study of the materials of our Palaeozoic and later detrital rocks 
may indicate that from very early times there has been a recur- 
rence of similar physical conditions, and that in geology also 
a recurrence of effects indicates a recurrence of the same 
causes. The facts which I have brought before you have justified, 
I trust, my opening remarks as to the rich harvest which yet 
awaits investigations into the structure of the fragmental rocks, 
To resume the simile then used, I see the land of promise, 
stretching far away from beneath my feet, till it seems to melt 
into the dim and as yet unknown distance. Not speedily will 
its riches be exhausted. Our hands will long have vanished, our 
voices will long have been still, before the work of discovery is 
ended, and men have reached the shore of that circumfluent 
ocean which, at least in this life, limits their finite powers. 
7 The considerable distance to which the clays extend in a southerly 
direction may possibly indicate that, to the east of Scotland, a communica- 
tion had now been opened with the northern ocean, which had set up a 
~ current along the coast east of tte Pennine Chain. 
? Asthe Speeton beds continue to be clays, one would infer a drift from 
the south, but a current to the opposite direction would be more probable, 
and it is the opinion of Dr. Sorby that this was the case. His papers 
“On the Direction of the Currents indicated by the Coarse Sediments 
= = British Rocks’’ are most valuable (Yorks. Geol. Pol. Soc. v. 220, 
c.)- 
3 The occasional beds of flint pebbles indicate a neighbouring shore line 
of Cretaceous rocks rather than the denudation of beds of Cretaceous age, 
which had been deposited on parts of the western land during the period of 
depression. 
SECTION D 
BIOLOGY 
OPENING ADDRESS BY WILLIAM CARRUTHERS, PRES.L.S., 
F.R.S., F.G.S., PRESIDENT OF THE SECTION 
In detaining you a few minutes from the proper work of the 
Section, I propose to ask your attention to what is known of 
the past history of the species of plants which still form a por- 
tion of the existing flora. The relation of our existing vegeta- 
tion to preceding floras is beyond the scope of our present 
inquiry: it has been frequently made the subject of exposition, 
but to handle it requires a more lively imagination than I can 
lay claim to, or, perhaps, than it is desirable to employ in any 
strictly scientific investigation. 
The literature of science is of little, if any, value in tracing the 
history of species, and in determining the modification or the 
persistency of characters which may be essential or accidental to 
them. If help could be obtained from this quarter, botanical 
inquiry would be specially favoured, for the literature of botany 
is earlier, and its terms have all along been more exact than in 
any of her sister sciences. But even the latest descriptions, in- 
corporating as they do the most advanced observations of 
science, and expressed in the most exact terminology, fail to 
supply the data on which a minute comparison of plants can be 
instituted. Any attempt to compare the descriptions of Linnzeus 
and the earlier systematists who, under his influence, introduced 
greater precision into their language, with the standard authors 
of our own day, would be of no value. The short, vague, and 
insufficient descriptions of the still earlier botanists cannot even 
be taken into consideration. 
Greater precision might be expected from the illustrations that 
have been in use in botanical literature from the earliest times ; 
but these really supply no better help in the minute study of 
species than the descriptions which they are intended to aid. 
The earliest illustrations are extremely rude: many of them are 
misplaced ; some are made to do duty for several species, and 
not a few are purely fictitious. The careful and minutely exact 
illustrations which are to be found in many modern systematic 
works are too recent to supply materials for detecting any 
changes that may have taken place in the elements of a flora. 
But the means of comparison which we look for in vain in the 
published literature of science may be found in the collections of 
dried plants which botanists have formed for several generations, 
The local herbaria of our own day represent not only the 
different species found in a country, but the various forms which 
occur, together with their distribution. They must supply the 
‘most certain materials for the minute comparison at any future 
epoch of the then existing vegetation with that of our own day. 
The preservation of dried plants as a help in the study of 
systematic botany was first employed in the middle of the six- 
teenth century. The earliest herbarium of which we have any 
record is that of John Falconer, an Enzlishman who travelled in 
Italy between 1540 and 1547, and who brought with him to 
England a collection of dried plants fastened in a book. This 
was seen by William Turner, our first British botanist, who 
refers to it in his ‘* Herbal,” published in 1551. Turner may 
have been already acquainted with this method of preserving 
plants, for in his enforced absence from England he studied at 
Bologna under Luca Ghini, the first Professor of Botany in 
Europe, who, there is reason to believe, originated the practice 
of making herbaria. Ghini’s pupils, Aldrovandus and Cz.- 
alpinus, formed extensive collections. Caspar Bauhin, whose 
‘©Prodromus” was the first attempt to digest the literature of 
botany, left a considerable herbarium, still preserved at Basle. 
No collection of English plants is known to exist older than the 
middle of the seventeenth century ; a volume containing some 
British and many exotic plants collected in the year 1647 was 
some years ago acquired by the British Museum. Towards the 
end of that century great activity was manifested in the collec- 
tion of plants, not only in our own country, but in every district 
of the globe visited by travellers. The labours of Ray and 
Sloane, of Petiver and Plukenet are manifest not only in the 
works which they published, but in the collections that they 
made, which were purchased by the country in 1759 when the 
museum of Sir Hans Sloane became the nucleus of the now 
extensive collections of the British Museum, The most im- 
portant of these collections in regard to British plants is the 
herbarium of Adam Buddle, collected nearly 200 years ago, and 
containing an extensive series, which formed the basis of a 
