British Islands, Shetland, Feroe, and Iceland. 51 



more than a seventh, and, finally, a tenth in Iceland. In 

 proportion, then, as we remove to a distance from Europe, 

 the number of vegetables peculiar to that continent dimi- 

 nishes ; but, at the same time, the proportion of the Green- 

 land plants increases very nearly in the same ratio. 



Completely agreeing with Mr Forbes as to the colonisa- 

 tion of the Islands of the North Sea, I yet demur at the bold- 

 ness and novelty of the hypothesis he has advanced. "With- 

 out interrogating the past history of the earth, I find in the 

 action of existing causes a plausible explanation of the trans- 

 port of the seeds of our continent to the nearest islands, and 

 from one islet to another, from England as far as Iceland. 



A great current, the Gulf Stream, has its source in the 

 Gulf of Mexico, runs along the shores of North America as 

 high as Newfoundland, then, traversing the Atlantic, washes 

 the western coasts of Scotland. It is this which conveys to 

 these coasts the seeds of Mexico, still endowed with the 

 power of germination — it is this which has thrown on the 

 shores of the Hebrides the Eriocaulon septangulare, a spe- 

 cies belonging to North America, the on]y one of all the 

 British plants which is not European. Running along the 

 coasts of Scotland, the Gulf Stream collects, so to speak, the 

 innumerable seeds which running waters convey to the sea, 

 and carries them along with it to sow them on the sandy 

 shores of Shetland, Feroe, and Iceland. This current ap- 

 pears to me to be the principal agent in the diffusion of 

 European plants in these islands ; and I do not hesitate to 

 ascribe to them the predominance of the flora of Europe 

 over that of North America. 



Winds, true aerial currents, likewise perform their part in 

 the dissemination of species, but like that of marine currents, 

 it escapes direct observation. Whoever has once encoun- 

 tered the long-continued and teijjrible winds of the north 

 seas, will no longer doubt that they are capable of transport- 

 ing, from one island to another, light seeds, often provided 

 with tufts of feathers and membranes which facilitate their 

 suspension in the air. A recent fact adds new strength to 

 this probability. On the 2d September 1845, at 9 o'clock in 

 the morning, there was an eruption of Mount Hecla, in Ice- 

 land. On the 3d, the ashes fell on the most southern islands 



