428 



NATURE 



\_Marcli 1, 1888 



It was, indeed, a fortunate circumstance that Darwin, after 

 being repelled by the narrow and soulless system of " geognosy " 

 taught by Jameson at Edinburgh, came at Cambridge under the 

 spell of Henslow, a man of most catholic taste, extensive ac- 

 quirements, and widest sympathy with all branches of natural 

 science. By intercourse with Henslow, Darwin's flagging in- 

 terest in science was rekindled and kept alive. It is a proud 

 boast for a University to have nourished the intellectual develop- 

 ment of Darwin ; and as that University has in the past 

 remained faithful to the memory of Newton, making his 

 mathematical teachings the characteristic and leading feature 

 of its studies, so, we may hope, it will in the future aim at that 

 complete union of geological and biological investigation of 

 which Darwin's labours constitute so grand an example. 



In the dedication of his "Journal of Researches," Darwin 

 acknowledged "with grateful pleasure" that "the chief part of 

 whatever scientific merit this journal and the other works of the 

 author may possess, has been derived from studying the well- 

 known and admirable ' Principles of Geology ' ; " and well do I 

 recollect how, in almost every conversation I had with him, he 

 would enlarge with warmth of feeling upon his indebtedness to 

 Lyell, not only for his lucid teaching, but for his constant and 

 helpful sympathy. How did he use to speak in terms of 

 reverence of his "master," and extol the magnanimity of one 

 who, though twelve years his senior, had abandoned slowly and 

 cautiously, as was the habit of his mind, yet in the end com- 

 pletely and ungrudgingly, his own conclusions and prepossessions, 

 and had accepted the doctrines of a pupil. 



Of Darwin's three geological books, the record of the ob- 

 servations made by him during the voyage of the Beagle, it is 

 impossible to speak in terms of praise that will seem, to those 

 acquainted with the merits of those admirable writings, as too 

 high ; and some portions of those works, especially the chapters 

 dealing with the great problem of foliation, are, I am convinced, 

 very far indeed from having i-eceived from geologists the amount 

 of attention which they deserve. 



After Darwin's return to England, in 1836, his attention was 

 for some years almost exclusively devoted to geological re- 

 searches ; and it was to this Society and to its officers that he 

 constantly came for help, advice, and sympathy. He writes at 

 this time, " If I was not more inclined for geology than the 

 other branches of natural history, I am sure Mr. Lyell's and 

 Lonsdale's kindness ought to fix me." 



Before reaching England, Darwin had written to Henslow 

 from St. Helena, on July 9, 1836, asking that he might be 

 proposed a Fellow of this Society, and on November 30 of 

 that year he was elected. In the following February he became 

 a member of our Council, and at the next anniversary, in 1838, 

 undertook the duties of Secretary. This office, after he had held 

 it for five years, he was compelled to resign through ill health : 

 but even after he had been driven from London through the 

 same cause, it was the evening meetings of this Society which 

 from time to time tempted him from the seclusion of Down, till 

 at last painful experience proved to him that he must forgo 

 even this too-exciting pleasure. Even after being compelled to 

 lay aside his hammer, when he had taken up scalpel and micro- 

 scope to study the Cirripedia, he did not forget the fossil forms 

 of the same group. 



Whether it was the distribution of organic forms in space, or 

 the order of their appearance in time, which had had most to do 

 in turning Darwin's thoughts into those currents which finally 

 led him to evolution, it would be idle to speculate ; but it may 

 safely be asserted that the geological aspects of natural history 

 had at least as much to do with the conception of the origin of 

 species as had the biological. 



How warm was Darwin's interest, all through his life, in the 

 progress of every branch of geological research may be gathered 

 from his letters to Lyell and other geological friends. In what 

 he had a presentiment would be, and which actually proved, his 

 latest work, "The Formation of Vegetable Mould through the 

 Action of Worms," he returned in his old age to a geological 

 problem which had occupied him during the years of his most 

 intimate connection with our Society. 



No memories can possibly have such fascination for myself as 

 those of the conversations which, during the last seven years of 

 his life, I was privileged to hold with Mr. Darwin upon the 

 current topics of geological interest. It was his habit when he 

 came to town, twice a year, to ask me to meet him, in order to 

 talk over geological questions, and thus I had opportunities for 

 close intercourse and discussion. No researches in our science 



were too minute, none too remote from the ordinary subjects of 

 his study, to engage his attention and command his sympathies. 

 How keenly did he recall the pleasures of his labours in this 

 Society, and the happiness of the friendships which he had 

 formed here ! How generously and with what warmth of 

 appreciation did he ever speak of the labours of those who had 

 succeeded him in endeavouring to carry out the objects of this 

 Society ! Of the gentleness, the sympathy, the contagious 

 enthusiasrn of the man, I dare not trust myself to speak ! 



At a time when there is perhaps some danger that the 

 excessive specialization which seems to have become a necessity 

 in both the geological and the biological sciences, may lead to 

 narrowness of view, restriction of aims, and petty jealousies 

 among the workers in circumscribed departments of those 

 sciences, it may be well to remember how Darwin, while 

 engaged in the most minute and detailed investigations upon 

 barnacles, earthworms, or pigeons, upon orchids, primroses, or 

 climbing plants, could ever keep his mind open to the influence 

 of each new discovery in every branch of geological and bio- 

 logical science. 



The great principles which lie at the foundation of modem 

 geology and of modern biology are the same ; and Darwin did 

 but furnish a new testament to the old covenant already accepted 

 by geologists. Now, more than ever in the history of natural 

 science, is there reason for the wjirmest sympathy, the most 

 thorough understanding, and the completest union in effort 

 between the cultivators of the geological and the biological 

 sciences. It is not by petulant unfaithfulness to the tried 

 methods of those two sciences, and a readiness to abandon the 

 principles which have led us to such real and important con- 

 quests, for the older methods that have been so often 

 discredited and found wanting, that we can hope to advance 

 those sciences. 



Lyell once wrote to Darwin as follows : " I really find, when 

 bringing up my preliminary essays in 'Principles' to the 

 science of the present day, so far as I know it, that the great 

 outline, and even most of the details, stand so uninjured, and 

 in many cases they are so much strengthened by new dis- 

 coveries, especially by yours, that we may begin to hope that 

 the great principles there insisted on will stand the test of new 

 discoveries." 



And to this Darwin replied with characteristic enthusiasm : — 



"Begin to hope? Why the possibility of a doubt has never 



crossed my mind for many a day. This may be very unphilo- 



sophical, but my geological salvation is staked upon it ! . . . It 



makes me quite indignant that you should talk of hoping.'" 



I^ifty years have elapsed since these words were written. How 

 infinitely more complicated seem to us the problems involved in 

 the explanation of the past by the study of the process going on 

 around us at present, than they possibly could have done to the 

 great pioneers of the Uniformitarian doctrines ! But the reasons 

 lor Lyell's hope and Darwin's confidence are still valid, nay, are 

 stronger than ever. For does not every new discovery remove 

 some difficulty or supply fresh illustrations of these views? May 

 every geologist to-day be endowed with a due share of Lyell's 

 caution ; but, for my own part, I see no reason why he should 

 not also possess a full portion of Darwin's faith. 



ON THE NUMBER OF DUST PARTICLES IN 

 THE A TMOSPHERE> 



AT the beginning of the paper, reference is made to the 

 ■^*- great advance recently achieved by physiologists, 

 regarding our knowledge of the solid matter floating in the 

 atmosphere, as they have already provided us with a consider- 

 able amount of information regarding the number of live germs 

 in the air under different conditions ; while we have but little 

 information regarding the dead organic and inorganic particles. 

 The following investigation was undertaken in the hope of 

 bringing the physical side of fhe subject abreast of the physio- 

 logical ; and in this paper is given an account of a method devised 

 by the author for counting the dust particles in the air, and also 

 some results obtained by means of it. 



One difficulty presented in this investigation is the extreme 

 minuteness of the particles to be counted ; most of them are 



' Communlc-ited by permission of the Coincil of the Royal Society of 

 Edinburgh, having been read to the Abstract Society on February 6, by John 

 Aitken, F.R.S.E. 



