June 10^th/56

I know not whether a few words in reference to Mr. Forbes’s views about former expanses of land, alluded to in your letter of 7^th., will be worth your trouble in reading them. ¹

The plants specially common to Ireland, S.W. England, W. France, Spain or Portugal, Azores,—or to two or more of these countries, & not general to Europe,—are precisely those, unadapted to bear continental climates.² They thrive in mild, humid, equable climates; are killed by low temperatures, or wither under dry heat; some bearing neither. Whatever the present dissevered & isolated distribution of these plants may suggest about former connexions between their present localities, unless assumed to be by intermediate hilly islands, the constitution or nature of the species physiologically, seems to negative. I know not a tittle of evidence to show that the species in question are of older creation or existence on the earth, than any others in Britain or Europe.—

The idea of a connexion between Europe & America, (whether quite continuous, or partially interrupted,) in high latitudes, seems rather supported than negatived by botanical facts.³ True, a good many plants of N.W. Europe are unknown in America; & vice versa. But (as a mere surmise, not investigated) if we could reduce the Ural chain to a few islands (like Iceland, Faroe &c.), & wash away much of the land on both sides, we should have a parallel case: diag 1 2 3

North Sea North

West & East

Europe islands Asiaramme

Many species would be in common to 1 & 3. Many peculiar to 1 or 3. Many of the common, & some of the peculiar, would be found in the islands of 2.

Forbes was not under the trammels of a very strict Conscience. He would be more likely to find “facts” to suit a conjecture, than those calculated to test its soundness. I should deem any one unwise who adapted his theories to Forbes’s statements of facts, unless those facts were verified afresh, or corroborated by others of like nature.⁴

Very faithfully | Hewett C. Watson To | C. Darwin | Esq