Dec. 13, 1888] 



NATURE 



161 



the length of the seconds penduhim as determined by Kater and 

 Sabine would thus be known accurately with reference to the 

 standard yard. It seemed to me that so important a scale should 

 hardly be sent away, even though in the care of so experienced 

 a physicist, without the authority of the Council, and without an 

 outer case being made for its box, which there was no time to get 



ady. The authority of the Council has since been obtained, 



id it fortunately happens that one of the assistants at the 



.leenwich Observatory is going to I'aris, who will take charge 



of the scale. Thus by the kind proposal of Commandant 



Deforges, we may shortly hope to have an authentic comparison 



of the length of the seconds pendulum as measured by Kater 



^ and Sabine with the standard English yard. 



At the time of the anniversary last year, some of the reports of 

 the observers who went to Grenada to observe the total solar 

 eclipse of August 1886 had been seen in, and I mentioned that 

 it seemed desirable, for convenience of reference at a future time, 

 that the different reports should come out together, instead of 

 being published in a scattered form, provided at least that the 

 waiting for the later reports should not cause too much delay. I 

 regret to say that the completion of the reports has been delnyed 

 in part by the illness of one of the observers, but I have every 

 hope that they will all be in by Christmas, and I do not anticipate 

 that any long time will elapse before they will be in some form 

 in the hands of the public. 



The time is well within our recollection when the occurrence 

 of the solar prominences seen in total eclipses first attracted the 

 attention of astronomers, and when for observations bearing on 

 their nature we had to wait for the rare and brief glimpses which, 

 clouds permitting, were afforded by total eclipses. Now, how- 

 ever, thanks to the method of observation devised independently 

 by Lockyer and Janssen, they may be studied at any time. It 

 would obviously be a great advantage if a similar study could be 

 made of the corona ; for though we cannot expect to obtain a 

 picture of it equal to that which may be got during a total 

 eclipse, yet, if a fairly good picture could be obtained from time 

 to lime, we might thereby be enabled to learn more about the 

 history of its changes than could be got by observations extend- 

 ing over a lifetime if restricted to total eclipses. Some observa- 

 tions were made during the partial phases of the last totfil 

 eclipse with the view of throwing light on the prospect of 

 success. Notwithstanding the unpromising nature of the results 

 obtained, I have reason for hoping that the desired object may 

 yet be accomplished. 



In addressing you last year, that year which will be memorable 

 as the Jubilee of the reign of our beloved Sovereign, I alluded 

 briefly to the progress which science had made in the last half- 

 century, and ventured to indicate one or two directions in which 

 it seemed to me possible that a very great addition to our 

 physical knowledge might some day be reached. I will not 

 to-day venture to look so far ahead ; but the mention of a total 

 eclipse leads me to refer to some theories now before the scientific 

 world which are likely to undergo full discussion and further 

 examination in the near future, with the probable result of a 

 pretty general agreement as to their acceptance or rejection. 



It is now many years since Dr. Huggins discovered the 

 peculiar character of the spectra of the nebulte, spectra which he 

 found to consist mainly of bright lines, indicating that what we 

 see is an incandescent gas. The natural supposition to make at 

 the time was that those distant masses of matter consisted of 

 incandescent gas, of which the luminosity was in some way kept 

 up, probably as a result of condensation. But the researches of 

 Mr. Lockyer, as described by him in the Uakerian Lecture which 

 he delivered last spring, and in part in a previous paper com- 

 municated shortly before the last anniversary, have led him to 

 take a different view of the constitution of nebulae. According 

 to the theory advanced by him, the mass of a nebula consists 

 mainly of meteorites, which are constantly coming into collision 

 here and there ; and the glowing gas the existence of which the 

 spectroscope reveals, is merely a portion of the matter, volatilized 

 by the heat of collision. According to the former view there- 

 fore, the nebula consists of glowing gas, not yet condensed into 

 a solid or liquid form, possibly in a condition even more ele- 

 mentary than that of the so-called elements that we know on 

 eaith ; according to the latter it consists mainly of discrete por- 

 tions of solid matter, and the glowing gas does not consist of 

 the same matter permanently glowing, but is continually supplied 

 afresh by fresh collisions. 



A similar theory is applied to explain the self-luminosity of 

 the nucleus, and sometimes the very root of the tail, of comets. 



A comet is regarded as a swarm of meteorites, moving in orbits 

 not greatly differing from one another ; and as the swarm 

 approaches the sun collisions become more frequent, and in- 

 dividually more potent, from an increase in the velocities, 

 differential as well as absolute, ; and a portion of matter is 

 volatilized and rendered incandescent. As to the tail, the 

 theory long ago suggested by Sir John Ilerschel has always 

 seemed to me by far the most probable of those that have been 

 advanced — namely, that it is due to the propulsion of excessively 

 attenuated matter, owing to a repulsive force, probably of 

 electrical origin, emanating from the sun. This view s^ems to 

 be adopted both by Mr. Lockyer and Dr. Huggins ; and the 

 latter gentleman, in an earlier Bakerian Lecture, has suggested a 

 new theory of the corona — the corona as distinguished from the 

 prominences — namely, that it is not projected from the sun by 

 molar forces due to the tremendous state of turmoil in which 

 we have very strong reason for believing that the matter com- 

 posing the sun exists, but of matter actually propelled from 

 the sun by a repulsive force in the manner of the tails of 

 comets. 



Daring as some of these speculations may appear to be, there 

 seems a great deal to recommend them, and the whole subject 

 is on.' of extreme interest at the present day. 



But I must not take up your time longer by dwelling on so 

 special a subject ; I proceed to matters more particularly 

 connected with the occasion on which we are assembled. 



The Council have awarded the Copley Medal of the year to 

 my predecessor in this chair, Mr. Huxley, for his investigations 

 on the morphology and histology of vertebrate and invertebrate 

 animals, and for his services to biological science in general 

 during many past years. These subjects lie so entirely out of 

 the range of my own studies that I need hardly say that in 

 attempting to give some idea of the more salient features of his 

 investigations 1 am dependent upon the kindness of biological 

 friends. 



During the fifteen or twenty years which preceded the publica- 

 tion of Darwin's famous work, the " Origin of Species," the 

 views and methods of comparative anatomists underwent a most 

 marked change. Without that change, biologists would have 

 been far less prepared to accept Mr. Darwin's work, and, what 

 is even more important, would have been unprepared to make 

 use of that work as a light enabling them to carry on the 

 remarkable researches which have so brilliantly characterized 

 the progress of biology during the last quarter of a century. 

 That change was effected chiefly by the labours first of Johannes 

 Midler, and subsequently of Huxley in this country, and of 

 Gegenbaur in Germany. The labours of these men opened out 

 the right road of morphological inquiry. It is not, perhaps, too 

 much to say that Mr. Huxley's treatment of his subject in his 

 "Morphology of Cephalous Mollusca " was to many young 

 morphologists little short of a revelation, and all his other works 

 of the same period, such as that on the Hydrozoa and on Tuni- 

 cates, and, later still, his treatment of the Vertebrate skull and 

 skeleton, and Arthropoda, produced in varying degree a like 

 effect. 



Closely allied to, or rather forming part of, his morphological 

 labours, are his numerous palaeontological researches, carried out 

 for the most part while he was Palsontologist to the Geological 

 Survey, researches characterized by the same clear morphological 

 insight, researches which have been as profitable to animal 

 morphology as useful to the geologist. The most important are 

 perhaps those on the remarkable reptiles of the Elgin Sand- 

 stones and on the Dinosauria ; but many others have great 

 value, and his anniversary address to the Geological Society, 

 in 1870, made its mark. 



Though his career has been in the main that of a morphologist, 

 he has through the common ground of histology given considerable 

 help to physiology. An early paper by him "On the Cell-Theory," 

 did much to clear away erroneous notions concerning the rela- 

 tions of structure to the actions of living beings. His article 

 on "Tegumentary Organs" was a great step onward as regards 

 both morphology and histology, and still remains a classical 

 work ; while, by other papers and in various ways, he has 

 contributed to the progress of histology and physiology. 



But, however important Mr. Huxley's original contributions to 

 the advancement of our scientific knowledge have been, we should 

 form a very inadequate idea of his benefits to the cause of science 

 if we did not bear in mind also his singular ability and effective- 

 ness as an expositor of science to the people, and the powerful 

 influence he has exerted in the improvement of the teaching of 



