and Coral Islands,” published in 1872. Darwin, in the preface to his second edition, candidly acknowledged that he had not previously laid sufficient weight on the mean temperature of the sea in determining the distribution of coral reefs; but this did not touch his main conception. In fact, he maintained his ground undisturbed, and at the same time admired greatly Dana’s book, which was the result of personal examination of more coral formations than perhaps any one man had ever studied, and which accepted Darwin’s fundamental proposition, that lagoon islands or atolls and barrier-reefs have been formed during periods of subsidence.5
No such strikingly original theory is propounded in the second part of “The Geology of the Beagle” dealing chiefly with volcanic islands. St. Jago, in the Cape de Verde Islands; Fernando Noronha, Terceira, Tahiti, Mauritius, St. Paul’s, Ascension, St. Helena, and the Galapagos are in turn more or less fully described, according to the opportunities the explorer had possessed. To some extent, as in the succeeding part, Darwin adapts his views on mountain elevation too closely to those enunciated by Elie de Beaumont. The third part of the geology of the Beagle, entitled “Geological Observations on South America,” was not published till 1846. Even this did not exhaust the contributions to geology made from the Beagle voyage, for it did not include the papers on the “Connection of certain Volcanic Phenomena in South America” (1838); on the “Distribution of Erratic Boulders” (1841); on the “Fine Dust which falls on Vessels” (1845); and on the “Geology of the Falkland Islands” (1846). A second edition of the two latter parts of “The Geology of the Beagle” was published in one volume in 1876.
Meanwhile, after spending a few years of his early married life in London, during which he was often in ill-health, Darwin fixed his residence in 1842 at Down House, near Beckenham, Kent. The little village of Down, three or four miles from the Orpington railway station, was near enough to London for convenient access, yet greatly secluded and thoroughly rural. The traveller’s roving days were over, and his infirmity of health prevented him from undertaking very fatiguing journeys. After the cessation of his active work for the Geological Society, Darwin’s chief public appearance was when he spoke at the Oxford meeting of the British Association, in 1847, when, strange to say, Ruskin was secretary of the Geological Section.
At Down then, situated some 400 feet above the sea level on a plateau of chalk, interrupted by wavy hollows with beech woods on the slopes, about forty years of Darwin’s life were passed. Down House, one of the square red brick mansions of the last century, to which have been since added a gable-fronted wing on one side and a more squarely-built wing and pillared portico on the other, is shut in and almost hidden from the roadway by a high wall and belt of trees. On the south side a walled garden opens into a quiet meadow, bounded by underwood, through which is seen a delightful view of the narrow valley beyond, towards Westerham.
One of the most admirable chapters of the well-known “Manual of Scientific Enquiry,” published in 1849, for the use of the navy and travellers generally, and edited by Sir John Herschel, was Darwin’s, on Geology. The explorer is here taught to make the most of his opportunities upon the soundest principles. The habits which the author had himself formed are inculcated upon the observer – copious collecting, accurate recording, much thinking. Nothing is omitted. Number-labels which can be read upside down must have a stop to indicate the right way up; every specimen should be ticketed on the day of collection; diagrams of all kinds should be made, as nearly as possible, to scale. “Acquire the habit of always seeking an explanation of every geological point met with.” “No one can expect to solve the many difficulties which will be encountered, and which for a long time will remain to perplex geologists; but a ray of light will occasionally be his reward, and the reward is ample.” Truly an ample reward awaited the observer who could thus speak of the value of “a ray of light;” he certainly did, to use the concluding words of the essay, “enjoy the high satisfaction of contributing to the perfection of the history of this wonderful world.”
Meanwhile Darwin had been carrying on a great research on the very peculiar order of crustacea, termed Cirripedia, better known as barnacles and acorn shells. He had originally only intended to describe a single abnormal member of the group, from South America, but was led, for the sake of comparison, to examine the internal parts of as many as possible. The British Museum collection was freely opened to him, and as the importance of studying the anatomy of many specimens became evident, the splendid collections of Messrs. Stutchbury, Cuming, and others were placed at his disposal, and he was permitted to open and to dissect unique specimens of great value. In fact, almost every naturalist of note who had any knowledge of the subject freely aided him, and the result was a masterly series of finely illustrated volumes; two on the living Cirripedia, issued by the Ray Society in 1851 and 1854; and two on the fossil Cirripedia of Great Britain, by the Palæontographical Society, published in the same years. There is evidence in these volumes that careful observations on the growth of these creatures had been made as far back as the visit to the Galapagos Islands in 1835. In many respects these works are as masterly as any the author ever wrote. Considering the previous obscurity of the subject, the difficulties attending the research, the almost entire lack at that time of any general microscopical knowledge of tissues, and especially of those of embryos, Darwin’s success is marvellous. The details are too technical for statement here, but any one with a zoological training, who studies the strange complication of the reproductive systems, and the remarkable transformations which the young undergo, as told in these volumes, will appreciate more than ever the breadth and the solidity of the basis of patiently acquired knowledge which Charles Darwin had accumulated while his “Origin of Species” was taking shape.
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