More Letters of Charles Darwin — Volume 1. Darwin Charles

Чтение книги онлайн.

СКАЧАТЬ week to working and writing out the flora question, for I now feel strong enough to give my promised evening lecture on it at the Royal Institution on Friday, and, moreover, wish to get it in printable form for the Reports of our Survey. Therefore at no time can I receive or answer objections with more benefit than now. From the hurry and pressure which unfortunately attend all my movements and doings I rarely have time to spare, in preparing for publication, to do more than give brief and unsatisfactory abstracts, which I fear are often extremely obscure.

      Now for your objections — which have sprung out of my own obscurities.

      I do not argue in a circle about the Irish case, but treat the botanical evidence of connection and the geological as distinct. The former only I urged at Cambridge; the latter I have not yet publicly maintained.

      My Cambridge argument (20/2. "On the Distribution of Endemic Plants," by E. Forbes, "Brit. Assoc. Rep." 1845 (Cambridge), page 67.) was this: That no known currents, whether of water or air, or ordinary means of transport (20/3. Darwin's note on transportation (found with Forbes' letter): "Forbes' arguments, from several Spanish plants in Ireland not being transported, not sound, because sea-currents and air ditto and migration of birds in SAME LINES. I have thought not-transportation the greatest difficulty. Now we see how many seeds every plant and tree requires to be regularly propagated in its own country, for we cannot think the great number of seeds superfluous, and therefore how small is the chance of here and there a solitary seedling being preserved in a well-stocked country."), would account for the little group of Asturian plants — few as to species, but playing a conspicuous part in the vegetation — giving a peculiar botanical character to the south of Ireland; that, as I had produced evidence of the other floras of our islands, i.e. the Germanic, the Cretaceous, and the Devonian (these terms used topographically, not geologically) having been acquired by migration over continuous land (the glacial or alpine flora I except for the present — as ice-carriage might have played a great part in its introduction) — I considered it most probable, and maintained, that the introduction of that Irish flora was also effected by the same means. I held also that the character of this flora was more southern and more ancient than that of any of the others, and that its fragmentary and limited state was probably due to the plants composing it having (from their comparative hardiness — heaths, saxifrages, etc.) survived the destroying influence of the glacial epoch.

      My geological argument now is as follows: half the Mediterranean islands, or more, are partly — in some cases (as Malta) wholly — composed of the upheaved bed of the Miocene sea; so is a great part of the south of France from Bordeaux to Montpellier; so is the west of Portugal; and we find the corresponding beds with the same fossils (Pecten latissimus, etc.) in the Azores. So general an upheaval seems to me to indicate the former existence of a great post-Miocene land {in} the region of what is usually called the Mediterranean flora. (Everywhere these Miocene islands, etc., bear a flora of true type.) If this land existed, it did not extend to America, for the fossils of the Miocene of America are representative and not identical. Where, then, was the edge or coast-line of it, Atlantic-wards? Look at the form and constancy of the great fucus-bank, and consider that it is a Sargassum bank, and that the Sargassum there is in an abnormal condition, and that the species of this genus of fuci are essentially ground-growers, and then see the probability of this bank having originated on a line of ancient coast.

      Now, having thus argued independently, first on my flora and second on the geological evidences of land in the quarter required, I put the two together to bear up my Irish case.

      I cannot admit the Sargassum case to be parallel with that of Confervae or Oscillatoria.

      I think I have evidence from the fossils of the boulder formations in Ireland that if such Miocene land existed it must have been broken up or partially broken up at the epoch of the glacial or boulder period.

      All objections thankfully received.

      Ever most sincerely,

      EDWARD FORBES.

      LETTER 21. TO L. JENYNS (BLOMEFIELD). Down. {1846}.

      I am much obliged for your note and kind intended present of your volume. (21/1. No doubt the late Mr. Blomefield's "Observations in Natural History." See "Life and Letters," II., page 31.) I feel sure I shall like it, for all discussions and observations on what the world would call trifling points in Natural History always appear to me very interesting. In such foreign periodicals as I have seen, there are no such papers as White, or Waterton, or some few other naturalists in Loudon's and Charlesworth's Journal, would have written; and a great loss it has always appeared to me. I should have much liked to have met you in London, but I cannot leave home, as my wife is recovering from a rather sharp fever attack, and I am myself slaving to finish my S. American Geology (21/2. "Geological Observations in South America" (London), 1846.), of which, thanks to all Plutonic powers, two-thirds are through the press, and then I shall feel a comparatively free man. Have you any thoughts of Southampton? (21/3. The British Association met at Southampton in 1846.) I have some vague idea of going there, and should much enjoy meeting you.

      LETTER 22. TO J.D. HOOKER. Shrewsbury {end of February 1846}.

      I came here on account of my father's health, which has been sadly failing of late, but to my great joy he has got surprisingly better...I had not heard of your botanical appointment (22/1. Sir Joseph was appointed Botanist to the Geological Survey in 1846.), and am very glad of it, more especially as it will make you travel and give you change of work and relaxation. Will you some time have to examine the Chalk and its junction with London Clay and Greensand? If so our house would be a good central place, and my horse would be at your disposal. Could you not spin a long week out of this examination? it would in truth delight us, and you could bring your papers (like Lyell) and work at odd times. Forbes has been writing to me about his subsidence doctrines; I wish I had heard his full details, but I have expressed to him in my ignorance my objections, which rest merely on its too great hypothetical basis; I shall be curious, when I meet him, to hear what he says. He is also speculating on the gulf-weed. I confess I cannot appreciate his reasoning about his Miocene continent, but I daresay it is from want of knowledge.

      You allude to the Sicily flora not being peculiar, and this being caused by its recent elevation (well established) in the main part: you will find Lyell has put forward this very clearly and well. The Apennines (which I was somewhere lately reading about) seems a very curious case.

      I think Forbes ought to allude a little to Lyell's (22/2. See Letter 19.) work on nearly the same subject as his speculations; not that I mean that Forbes wishes to take the smallest credit from him or any man alive; no man, as far as I see, likes so much to give credit to others, or more soars above the petty craving for self-celebrity.

      If you come to any more conclusions about polymorphism, I should be very glad to hear the result: it is delightful to have many points fermenting in one's brain, and your letters and conclusions always give one plenty of this same fermentation. I wish I could even make any return for all your facts, views, and suggestions.

      LETTER 23. TO J.D. HOOKER.

      (23/1. The following extract gives the germ of what developed into an interesting discussion in the "Origin" (Edition I., page 147). Darwin wrote, "I suspect also that some cases of compensation which have been advanced and likewise some other facts, may be merged under a more general principle: namely, that natural selection is continually trying to economise in every part of the organism." He speaks of the general belief of botanists in compensation, but does not quote any instances.)

      {September 1846}.

      Have you ever thought of G. St. Hilaire's "loi de balancement" (23/2. According to Darwin ("Variation of Animals and Plants," 2nd edition, II., page 335) the law of balancement was propounded by Goethe СКАЧАТЬ