[Enclosure]

p. 46.— I am sure that I have read of a Mus from Viti Is^d, but this may have been introduced. I am nearly sure that Günther has described Mammals from New Hebrides, & French-man from New Caledonia, but perhaps you w^d hardly call latter oceanic Is^d4

p. 68 I most heartily concur about separated genera of same family: I cautioned Günther on this account before he published his Tortoise paper.⁵

p. 72 You probably know more than I do about distribution of Land Mollusca over Pacific, but I think there must be some far more effective means of dispersal than rafts, or floating trees. D^r. Gould showed how every islet in the Pacific has land-shells.⁶

p. 157 I heartily agree about N. Zealand. When Hutton speaking of the extinction of all temperate forms during a glacial period, he overlooks probability (as it seems to me) of former land (or approximate island^s) communication to the North, whence, as I suspect, N. Zealand was formerly stocked.—⁷

p. 172 Is it not rather rash to refer paucity of fossils to coldness of waters, seeing how wonderfully rich the bottom of sea has just proved off the N. coast of Siberia,—not to mention the abyssal regions of the great oceans. May not paucity be due to the stirring up of the bottom by icebergs?⁸

With respect to your Glacial Chapt^r., my opinion is worth very little, as the subject is so difficult. But as far as I can judge, your view seems the most probable ever suggested.⁹ Until reading your book, I had quite rejected the Lyellian doctrine, but joined to the influence of the form of the land on sea-currents the case has a very different aspect.¹⁰ I had also felt a good deal of difficulty in Croll’s views, as far as I could follow them.¹¹ I think that you have rendered improbable any great number of true glacial periods.¹² I still feel much difficulty about the plants & great Saurians &c of the Arctic regions.¹³ If much warm water was poured into the Arctic basin & got chilled, would not the return currents lower the temp^re of whole tropical seas (or are these too extensive) & so lessen your source of heat. It seems to me a serious omission that you do not explain what geograph. change coincided with or caused the cessation of the last glacial period; for if it was caused by coincident excentricity & geograph. changes, its cessation would equally require geograph. changes. From my son George,¹⁴ who read these chapters with much interest, & admired the clearness & vigour of the discussion, I could not extract any judgment, on account of the many doubtful meteorological points. He demurs to your use of term “epoch”, & says that in astronomy it is used for a definite point of time & not for a period.— One speaks of an epoch in history.—

Chapter X. I cannot feel content with your 28 million years, but solely on geological grounds (*see addendum)—viz when I think of the Chalk—successive coal-beds—nummulitic rocks, & a wide-spread of conglomerate in Andes, which I estimated at least of 10,000 ft in thickness.— But my chief difficulty lies in the cases where one side of fault in solid rock has been raised above 10,000 ft. & yet the surface betrays nothing & resembles that of the whole surrounding country. This amt of denudation at your rate of 1 ft per 3000 years would require 30 million of years; & during many a long period the surface must have been submerged & saved from wear & tear.¹⁵

It might be argued that you overestimate the importance of climatal changes & migration in the modification of species, unless you guard yourself by saying that it applies only where there is no retreat for them. For how little the marine molluscs have changed since before glacial period! I accounted for this fact by their having slowly migrated all in a body together, as I believe that the interaction of organisms is much more important than climatal changes.

Azores. The discussion seems to me excellent.¹⁶   I formerly came to same conclusion with you, but believe that I attributed a little more to stranded icebergs & coast-ice, for I have a vague remembrance of some glacial deposit on northern shores.—¹⁷ God knows where the reference is. I have, also, somewhere a M.S. on the straggling birds, sent to me in answer to a letter on subject, by a scientific consul there, many years ago.—¹⁸

Galapagos.— I regret that you have not discussed plants. Perhaps I overvalue these Isl^s, for how they did interest me & how they have influenced my life, as one main element of my attending to origin of species.

You see that I have gone on writing as I read, & on almost next page there comes discussion of Galapagos Flora!¹⁹

(p. 295. No doubt preoccupation with plants is very important; but if a new form has any considerable advantage it tells, as I believe, very little. I have read several accounts of European plants occupying ground, in New Zealand, which had never been touched by the hand of man.— So with guava bushes in Tahiti.— But the Pampas offers the most flagrant instance against what you say.—²⁰

Ch. Gr. Britain. This seems to me first rate & includes very much matter quite new to me.— How curious about the Irish F.W. fishes! As your book will be sure to run through several editions, I advise you to look to changes in trout (due to direct action of conditions) in different rivers in N. Zealand in course of some 10 years.— See “Arthur in Transact N. Zealand Institute Vol XI 1878 p. 284.”—²¹

p.   You might possibly like to hear that it is said in the “Voyage a l’isle de France par un Officier du Roi” who visited the island in 1870 that a fresh-water fish the Gourami had been introduced from Batavia & had multiplied (as well as Gold-fishes) in Mauritius. He also says (p. 170) “On a essayé, mais sans succès, d’y transporter des grenouilles, qui mangent les œufs que les moustiques deposent sur les eaux stagnantes”. It thus appears that there then were no frogs on island.—²²

This Madagascan Ch: seems to me one of best in book. How well you show here & elsewhere the importance of changes in the inhabitants of the adjoining continent. I hope that you have destroyed Lemuria for ever: I never believed in it for a minute.²³

I am quite inclined to believe in your Australian views; they are wonderfully ingenious, but almost too audacious for me. My old brain, perhaps, is too weak to grasp so many new ideas.— I was quite prepared for the former northern & southern extension of N. Zealand, I used to think with New Caledonia. The most startling of all your views is that of stocking the former Antarctic continent, viâ Tierra del Fuego, with northern forms, & thence N. Zealand & S. Australia.²⁴ This gives me a shudder from its boldness. With respect to absence of Australian trees, I remember that A. De Candolle shows that they from some cause spread less than herbs.²⁵

Ch XXIII. is rather too speculative for my old noddle.— I must think that you overrate importance of new surfaces on mountains & dispersal from mountain to mountain.— I still believe in alpine plants having lived on the lowlands & in the northern tropical regions having been cooled during glacial period, & thus only can I understand character of floras on the isolated African mountains. It appears to me that you are not justified in arguing from dispersal to oceanic islands to mountains. Not only in latter cases currents of sea are absent, but what is there to make birds fly direct from one alpine summit to another? There is left only storms of wind, & if it probable or possible that seeds may thus be carried for great distances, I do not believe that there is at present any evidence of their being thus carried more than a few miles.—²⁶

* Addendum to p.3

It seems to me (not that I have been able to think out the whole case) that the problem (as far as age is judged of by the thickness of our formations) is the rate of deposition over areas of subsidence, & not near the coast over the world; for beneath the Tertiary beds most of the formations appear to have been deposited during subsidence. I must confess, however, that I have never succeeded in realising what the conditions were & whence all the sediment came, during the deposition of the enormous Carboniferous formation.— During elevation I believe that the shore deposits are raised up & distributed again & again; & that near the mouths of great rivers the land is added to; but I doubt whether our Secondary & palæozoic formations (except the Neocomian) were deposited as estuaries & growing low land.