326 



NA TURE 



[August 2, 1906 



visible to the naked eye may be stated as eight thousand ; 

 this is raised by the use of our best telescopes to a hun- 

 dred million. But the number which can be photographed 

 is indefinite and depends on length of exposure : a thousand 

 million can certainly be so recorded. 



The serious practical proposal to " chart the sliy " by 

 means of photography certainly dates from this side of 

 1881. The Paris Conference of 1887, which made an inter- 

 national scheme for sharing the sky among eighteen obser- 

 vatories (still busy with tlie work, and producing excellent 

 results), originated with photographs of the comet of 1882, 

 taken at the Cape Observatory. 



Prof. Pickering, of Harvard, did not join this coopera- 

 tive scheme, but has gradually devised methods of charting 

 the sky very rapidly, so that he has at Harvard records of 

 the whole sky many times over, and when new objects are 

 discovered he can trace their history backwards for more 

 than a dozen years by reference to his plates. This is a 

 wonderful new method, a mode of keeping record of present 

 movements and changes which promises much for the future 

 of astronomy. By the photographic method hundreds of 

 new variable stars and other interesting objects have been 

 discovered. New planets have been detected by the hundred. 

 Up to 1S81 two hundred and twenty were known. In 1881 

 only one was found ; namely, Stephania, being No. 220, 

 discovered on May ig. Now a score at least are discovered 

 every year. More than five hundred are now known. One 

 of these — Eros (No. 433) — is particularly interesting, since it 

 is nearer to the sun than is Mars, and gives a splendid 

 opportunity for fixing with increased accuracy the sun's 

 distance from the earth. Two new satellites to Saturn and 

 two to Jupiter have been discovered by photography (besides 

 one to Jupiter in 1892 by the visual telescope of the Lick 

 Observatory). One of the new satellites of Saturn goes 

 round that planet the -wrong way, thus calling for a 

 fundamental revision of our ideas of the origin of the solar 

 system. 



The introduction of photography has made an immense 

 difference in spectroscopic work. The spectra of the stars 

 have been readily mapped out and classified, and now the 

 motions in the line of sight of faint stars can be deter- 

 rnined. This " motion in the line of sight," which was 

 discernible but scarcely measurable with accuracy before, 

 now provides one of the most refined methods in astronomy 

 for ascertaining the dimensions and motions of the 

 universe. It gives us velocities in miles per second instead 

 of in an angular unit to be interpreted by a very imperfect 

 knowledge of the star's distance. The method was in 

 188 1 a mere curiosity, which Huggins was almost alone in 

 having examined, though visual measures had been begun 

 at Greenwich in 1875, and were continued for many years, 

 only to be ultimately found to be affected by systematic 

 error. The photographic method started by V'ogel in 1887 

 really has made all the difference, and this work is now a 

 vast department of astronomical industry. Among other 

 by-products of the method are the " spectroscopic doubles," 

 stars which we know to be double, and of which we can 

 determine the period of revolution, though we cannot 

 separate them visually by the greatest telescope. 



Work on the sun has been entirely revolutionised by the 

 use of photography. The last decade has seen the invention 

 of the spectroheliograph — which simply means that astrono- 

 mers can now study in detail portions of the sun of which 

 Ihey could previously only get a bare indication. 



More of the same story could be related, but enough has 

 been said to show how full of life and progress is this 

 most ancient and imposing of all sciences. 



A minor though very important influence in the progress 

 of astronomy has been the provision, by the expenditure of 

 great wealth in America, of great telescopes and equipments. 



In 1877 my distinguished predecessor in the presidency of 

 the British Association started a line of mathematical re- 

 search which has been very fruitful and is of great future 

 promise for astronomy. He was able himself last year to 

 give some account of this research to the Association. On 

 the present occasion I may mention that as recently as last 

 .'\pril, at the Royal Astronomical Society, two important 

 papers were read — one by Mr. Cowell and the other by Mr. 

 Stratton — which have their roots in Sir George Darwin's 

 work. The former was led to suggest that the day is 

 lengthening ten times as rapidly as had been supposed, and 



NO. 191 8, VOL. 74] 



the latter showed that in all probability the planets had 

 all turned upside down since their birth. 



And yet M. Brunettiere and his friends wish us to believe 

 that science is bankrupt, and has no new things in store for 

 humanity. 



Geology. — In the field of geological research the main 

 feature in the past twenty-five years has been the increasing 

 acceptance of the evolutionary as contrasted with the uni- 

 formitarian view of geological phenomena. The great work 

 of Suess, " Das Antlitz der Erde," is undoubtedly the most 

 important contribution to physical geology within the period. 

 The first volume appeared in 1885, and the impetus which 

 it has given to the science may be judged by the epithet 

 applied to the views for which Suess is responsible — "the 

 New Geology." Suess attempts to trace the orderly sequence 

 of the principal changes in the earth's crust since it first 

 began to form. He strongly opposes the old theory of 

 elevation, and accounts for the movements as due to dif- 

 ferential collapse of the crust, accompanied by folding due 

 to tangential stress. Among special results gained by 

 geologists in the period we survey may be cited new views 

 as to the origin of the crystalline schists, favouring a 

 return to something like the hypogone origin advocated by 

 Lyell ; the facts as to deep-sea deposits, now in course of 

 formation, embodied in the " Challenger " reports on that 

 subject; the increasing discrimination and tracking of those 

 minor divisio'ns of strata called " zones"; the assignment 

 of the Olenellus fauna of Cambrian age to a position earlier 

 than that of the Paradoxides fauna; the discovery of 

 Radiolaria in Palaiozoic rocks by special methods of examin- 

 ation, and the recognition of Graptolites as indices of 

 geological horizons in lower Pakeozoic beds. Glacially 

 eroded rocks in Boulder-clays of Permo-Carboniferous age 

 have been recognised in many parts of the world {e.g. 

 .\ustralia and South Africa), and thus the view put forward 

 by W. T. Blanford as to the occurrence of the same 

 phenomena in conglomerates of this age in India is con- 

 firmed. Eozoon is finally abandoned as owing its structure 

 to an organism. The oldest fossiliferous beds known to us 

 are still far from the beginning of life. They contain a 

 highly developed and varied animal fauna — and something 

 like the whole of the older moiety of rocks of aqueous 

 origin have failed as yet to present us with any remains of 

 the animals or plants which must have inhabited the seas 

 which deposited them. The boring of a coral reef initiated 

 by Prof. .Sollas at the Nottingham meeting of this 

 Association in 1893 was successfully carried out, and a 

 depth of 1114J feet reached. Information of great value 

 to geologists was thus obtained. 



.Animal and Vegetable Morphography. — Were I to attempt 

 to give an account of the new kinds of aninlals and plants 

 discovered since 1881, I should have to read out a bare 

 catalogue, for time would not allow me to explain the 

 interest attaching to each. Explorers have been busy in 

 all parts of. the world — in Central Africa, in the Antarctic, 

 in remote parts of China, in Patagonia and Australia, and 

 on the floor of the ocean, as well as in caverns, on moun- 

 tain tops, and in great lakes and rivers. We have learnt 

 much that is new as to distribution ; countless new forms 

 have been discovered, and careful anatomical and micro- 

 scopical study conducted on specimens sent home to our 

 laboratories. I cannot refrain from calling to mind the 

 discovery of the eggs of the Australian duckmole and 

 hedgehog; the fresh-water jelly-fish of Regent's Park, the 

 African lakes, and the Delaware River ; the marsupial mole 

 of Central Australia ; the okapi ; the young and adult of the 

 mud-fishes of Australia. Africa, and South America; the 

 fishes of the Nile and Congo ; the gill-bearing earthworms 

 and mud-worms ; the various forms of the caterpillar-like 

 Peripatus ; strange deep-sea fishes, polyps and sponges. 



The main result of a good deal of such investigation 

 is measured by our increased knowledge of the pedigree of 

 organisms, what used to be called "classification." The 

 anatomical study by the Australian professors. Hill and 

 Wilson, of the teeth and the foetus of the Australian group 

 of pouched mammals — the marsupials — has entirely upset 

 previous notions, to the effect that these were a primitive 

 group, and has shown that their possession of only one 

 replacing tooth is a retention of one out of many such teeth 

 (the germs of which are present), as in placental mammals ; 

 and further that many of these marsupials have the nourish- 



