darwin and modern science-第88章
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The second period of Darwin's geological careerthe five years spent by him on board the 〃Beagle〃was the one in which by far the most important stage in his mental development was accomplished。 He left England a healthy； vigorous and enthusiastic collector； he returned five years later with unique experiences； the germs of great ideas； and a knowledge which placed him at once in the foremost ranks of the geologists of that day。 Huxley has well said that 〃Darwin found on board the 〃Beagle〃 that which neither the pedagogues of Shrewsbury； nor the professoriate of Edinburgh； nor the tutors of Cambridge had managed to give him。〃 （〃Proc。 Roy。 Soc。〃 Vol。 XLIV。 （1888）； page IX。） Darwin himself wrote； referring to the date at which the voyage was expected to begin： 〃My second life will then commence； and it shall be as a birthday for the rest of my life。〃 （〃L。L。〃 I。 page 214。）； and looking back on the voyage after forty years； he wrote； 〃The voyage of the 'Beagle' has been by far the most important event in my life； and has determined my whole career；。。。I have always felt that I owe to the voyage the first real training or education of my mind； I was led to attend closely to several branches of natural history； and thus my powers of observation were improved； though they were always fairly developed。〃 （〃L。L。〃 I。 page 61。）
Referring to these general studies in natural history； however； Darwin adds a very significant remark： 〃The investigation of the geology of the places visited was far more important； as reasoning here comes into play。 On first examining a new district nothing can appear more hopeless than the chaos of rocks； but by recording the stratification and nature of the rocks and fossils at many points； always reasoning and predicting what will be found elsewhere； light soon begins to dawn on the district； and the structure of the whole becomes more or less intelligible。〃 （〃L。L。〃 I。 page 62。）
The famous voyage began amid doubts； discouragements and disappointments。 Fearful of heart…disease； sad at parting from home and friends； depressed by sea…sickness； the young explorer； after being twice driven back by baffling winds； reached the great object of his ambition； the island of Teneriffe； only to find that； owing to quarantine regulations； landing was out of the question。
But soon this inauspicious opening of the voyage was forgotten。 Henslow had advised his pupil to take with him the first volume of Lyell's 〃Principles of Geology〃； then just publishedbut cautioned him （as nearly all the leaders in geological science at that day would certainly have done） 〃on no account to accept the views therein advocated。〃 （〃L。L。〃 I。 page 73。） It is probable that the days of waiting； discomfort and sea… sickness at the beginning of the voyage were relieved by the reading of this volume。 For he says that when he landed； three weeks after setting sail from Plymouth； in St Jago； the largest of the Cape de Verde Islands； the volume had already been 〃studied attentively； and the book was of the highest service to me in many ways。。。〃 His first original geological work； he declares； 〃showed me clearly the wonderful superiority of Lyell's manner of treating geology； compared with that of any other author； whose works I had with me or ever afterwards read。〃 （〃L。L。〃 I。 page 62。）
At St Jago Darwin first experienced the joy of making new discoveries； and his delight was unbounded。 Writing to his father he says； 〃Geologising in a volcanic country is most delightful； besides the interest attached to itself； it leads you into most beautiful and retired spots。〃 （〃L。L。〃 I。 page 228。） To Henslow he wrote of St Jago： 〃Here we spent three most delightful weeks。。。St Jago is singularly barren； and produces few plants or insects； so that my hammer was my usual companion； and in its company most delightful hours I spent。〃 〃The geology was pre…eminently interesting； and I believe quite new； there are some facts on a large scale of upraised coast （which is an excellent epoch for all the volcanic rocks to date from）； that would interest Mr Lyell。〃 （〃L。L。〃 I。 page 235。） After more than forty years the memory of this； his first geological work； seems as fresh as ever； and he wrote in 1876； 〃The geology of St Jago is very striking； yet simple： a stream of lava formerly flowed over the bed of the sea； formed of triturated recent shells and corals； which it has baked into a hard white rock。 Since then the whole island has been upheaved。 But the line of white rock revealed to me a new and important fact； namely； that there had been afterwards subsidence round the craters； which had since been in action； and had poured forth lava。〃 （〃L。L。〃 I。 page 65。）
It was at this time； probably； that Darwin made his first attempt at drawing a sketch…map and section to illustrate the observations he had made （see his 〃Volcanic Islands〃； pages 1 and 9）。 His first important geological discovery； that of the subsidence of strata around volcanic vents （which has since been confirmed by Mr Heaphy in New Zealand and other authors） awakened an intense enthusiasm； and he writes： 〃It then first dawned on me that I might perhaps write a book on the geology of the various countries visited； and this made me thrill with delight。 That was a memorable hour to me； and how distinctly I can call to mind the low cliff of lava beneath which I rested； with the sun glaring hot； a few strange desert plants growing near； and with living corals in the tidal pools at my feet。〃 （〃L。L。〃 I。 page 66。）
But it was when the 〃Beagle〃； after touching at St Paul's rock and Tristan d'Acunha （for a sufficient time only to collect specimens）； reached the shores of South America； that Darwin's real work began； and he was able； while the marine surveys were in progress； to make many extensive journeys on land。 His letters at this time show that geology had become his chief delight； and such exclamations as 〃Geology carries the day；〃 〃I find in Geology a never failing interest；〃 etc。 abound in his correspondence。
Darwin's time was divided between the study of the great deposits of red mudthe Pampean formationwith its interesting fossil bones and shells affording proofs of slow and constant movements of the land； and the underlying masses of metamorphic and plutonic rocks。 Writing to Henslow in March； 1834； he says： 〃I am quite charmed with Geology； but； like the wise animal between two bundles of hay； I do not know which to like best； the old crystalline groups of rocks； or the softer and fossiliferous beds。 When puzzling about stratification； etc。； I feel inclined to cry 'a fig for your big oysters； and your bigger megatheriums。' But then when digging out some fine bones； I wonder how any man can tire his arms with hammering granite。〃 （〃L。L。〃 I。 page 249。） We are told by Darwin that he loved to reason about and attempt to predict the nature of the rocks in each new district before he arrived at it。
This love of guessing as to the geology of a district he was about to visit is amusingly expressed by him in a letter （of May； 1832） to his cousin and old college…friend； Fox。 After alluding to the beetles he had been collectinga taste his friend had in common with himselfhe writes of geology that 〃It is like the pleasure of gambling。 Speculating on first arriving； what the rocks may be； I often mentally cry out 3 to 1 tertiary against primitive； but the latter have hitherto won all the bets。〃 （〃L。L。〃 I。 page 233。）
Not the least important of the educational results of the voyage to Darwin was the acquirement by him of those habits of industry and method which enabled him in after life to accomplish so muchin spite of constant failures of health。 From the outset； he daily undertook and resolutely accomplished； in spite of sea…sickness and other distractions； four important tasks。 In the first place he regularly wrote up the pages of his Journal； in which； paying great attention to literary style and composition； he recorded only matters that would be of general interest； such as remarks on scenery and vegetation； on the peculiarities and habits of animals； and on the characters； avocations and political institutions of the various races of men with whom he was brought in contact。 It was the freshness of these observations that gave his 〃Narrative〃 so much charm。 Only in those cases in which his ideas had become fully crystallised； did he attempt to deal with scientific matters in this journal。 His second task was to write in voluminous note…books facts concerning animals and plants； collected on sea or land； which could not be well made out from specimens preserved in spirit； but he tells us that； owing to want of skill in dissecting and drawing； much of the time spent in this work was entirely thrown away； 〃a great pile of MS。 which I made during the voyage has proved almost useless。〃 （〃L。L。〃 I。 page 62。） Huxley confirmed this judgment on his biological work； declaring that 〃all his zeal and industry resulted； for the most part； in a vast accumulation of useless manuscript。〃 （〃Proc。 Roy。 Soc。〃 Vol。 XLIV。 （1888）； page IX。） Darwin's third task was of a very different character and of infinitely greater value。 It consisted in writing notes of his journeys on landthe notes being devoted to the geology of the districts visited by him。 These formed the basis； not only of a number of geological papers published on his return； but also of the three important volumes forming 〃The Geology of the voyage of the 'Beagle'〃。 On July 24th； 1834； when little more than half of the voyage had been completed； Darwin wrote to Henslow； 〃My notes are becoming bulky。 I have about 600 small quarto pages full； about half of this is Geology。〃 （〃M。L。〃 I。 page 14。） The last； and certainly not the least important of all his duties； consisted in numbering； cataloguing； and packing his specimens for despatch to Henslow； who had undertaken the care of them。 In his letters he often expresses the greatest solicitude lest the value of these specimens should be impaired by the removal of the numbers corresponding to his manuscript lists。 Science owes much to Henslow's patient care of the collections sent to him by Darwin。 The latter wrote in Henslow's biography； 〃During the five years' voyage； he regularly corresponded with me and guided my efforts； he received； opened； and took care of all the specimens sent home in many large boxes。〃 （〃Life of Henslow〃； by L。 Jenyns （Blomefield）； London； 1862； page 53。）
Darwin's geological specimens are now very appropriately lodged for the most part in the Sedgwick Museum； Cambridge； his original Catalogue with subsequent annotations being preserved with them。 From an examination of these catalogues and specimens we are able to form a fair notion of the work done by Darwin in his little cabin in the 〃Beagle〃； in the intervals between his land journeys。
Besides writing up his notes； it is evident that he was able to accomplish a considerable amount of study of his specimens； before they were packed up for despatch to Henslow。 Besides hand…magnifiers and a microscope； Darwin had an equipment for blowpipe…analysis； a contact…goniometer and magnet； and these were in constant use by him。 His small library of reference （now included in the Collection of books pla
