To John Phillips [12? March 1848]
Down Farnborough Kent
My dear Phillips
I am extremely much obliged by your full & most satisfactory note. I instantly turned to Lardner’s Encyclop.,1 & there found every point, put as clear as daylight, as if in answer to my mental queries. It was uncommonly stupid my not looking there before, for on rereading it, I remembered well having formerly been much interested by all that you had written on this subject.—2 I am not going to discuss the general question of erratics, but only the one point of their transport from a lower to a higher level, & secondarily the gradual diminution of the size of the boulders in going from their parent source.—3 My notion will at first strike you as monstrous but when worked out, I feel sure, whether true or not, it will not appear monstrous. It is that the boulders have been transported by coast-ice, & not by icebergs (a distinction which will, I believe explain many points & which I briefly noticed in my paper on the Erratics of the southern hemisphere)4 & that during the period of such transportal, the level of the land was subsiding. If you will call to mind the manner, as described by Bayfield & Bowen in Lyell’s principles,5 in which coast-ice on the N. American shore, annually acts, you will at once perceive, how the boulders will rise, as the land sinks, or rather not to speak paradoxically, how the boulders are kept at the same level, whilst the land sinks. If this can be proved true, it will be pretty, for it will allow us to measure to a foot the amount of subsidence, during the glacial period: thus I have no doubt that the Lake district subsided at least 900 feet; each winter your Conglomerate boulders, being pushed (so to speak) an inch or so upwards.— Some objections will occur to you at once; but I think can I answer the more obvious ones.—
You most kindly offer me any further information: literally one line will answer me, are the upper conglomerate boulders, which now stand about, say from 700 to 900 feet above their parent rock, (I do not care about the others) rounded or angular. Hopkins speaks of all those in neighbourhood of Stainmoor as being well rounded.— It is very probable that you may not have attended to the state especially of the conglomerate boulders, & therefore to save you writing, I shall understand, if I do not hear, that you cannot answer me.—6
Most sincerely yours | C. Darwin
Hopkins does not speak so much as if he himself doubted the identification of the conglomerate boulders, but as if some one else had; but he seldom condescends to give references: nor, I suspect, does he read much:—if he had read your statements in Lardner, he cd not have doubted.—
Thanks JP for his note and reference. CD’s paper will not deal with the general question of erratics but only their transportal from a lower to a higher level ["The transportal of erratic boulders", Collected papers 1: 218–27]. His notion is that the boulders were transported by coast-ice, not drifting icebergs, and that during the period of transportal the land was subsiding. Can JP tell him whether the raised conglomerate boulders he observed were rounded or angular?