OEIGIN OF LOCAL FLOEAS. 
29 
already accunmlated^ and from tlie progress that has been 
already made^ investigations of this nature would seem to be 
quite within the scope of human inquiry and successful scien- 
tific research. 
It is obvious that all hypotheses which aim at connecting the 
present with the former state of things, to be valid and satis- 
factory, must be founded on correct data in geology and 
palseontology. Professor Forbes was the first to lead the way 
in these difficult and interesting* explorations, in his essay On 
the Connection subsisting between the Distribution of the 
existing Fauna and Flora of the British Isles, and the Oeo- 
logical Changes which have affected their Area, especially 
during the Epoch of the Northern Drift.'’^ 
Some islands possess a ffora peculiar to themselves, and form 
distinct centres of vegetation, whilst others contain only the 
plants common to the nearest continent. The latter is the 
case with Great Britain, Ireland, and the adjacent isles, which, 
with one exception, are stocked with the plants of the adjacent 
continent of Europe. The exception is Uriocaulon septangulare 
(jointed pipe- wort), found only in the Hebrides, and Conne- 
mara, in the west of Ireland, and not known elsewhere in 
Europe. It is a North American plant, and has no doubt 
been introduced naturally into the British isles, by means of 
transport, now or anciently in action.'’^ 
The British isles have been explored by geologists, and they 
have discovered indications which amount to positive proofs 
that they were formerly united to Europe. England makes 
the nearest approach to the Continent at Folkestone, in Kent, 
which is not more than twenty miles distant from Cape Grisnez 
on the coast of France. The former union of the two coun- 
tries by an isthmus, which has been wasted away by the denud- 
ing force of the waves, is indicated by the shallowness of the 
intervening strait, the proximity and identity in mineral com- 
position of the opposite shores and cliffs, whether ffat or sandy, 
steep or chalky, and the occurrence of a submarine ridge, 
running across the channel. 
According to Professor Forbes, there are three modes in 
which an isolated area may become peopled by plants and 
animals. 
1. By special creation within the area. 
2. By transport to it. 
3. By migration before isolation.-’^ 
As to the first of these modes, it is unnecessary, for, as the 
plants of Great Britain are, with the single exception already 
mentioned, all identically the same as those in Europe, there is 
no occasion to account for then* existence in England and Ire- 
land by the theory of their special creation within the area,^^ 
