572 



NA TURE 



[August 17, 1905 



ment of corpusdes. Accordingly we may state that de- 

 finite numbers of corpuscles are capable of association in 

 stable communities of definite types. 



An infinite number of communities are possible, possess- 

 ing greater or lesser degrees of stability. Thus the cor- 

 puscles in one sucfi community might make thousands of 

 revolutions in their orbits before instability declared itself ; 

 such an atom might perhaps last for a long time as esti- 

 mated in millionths of seconds, but it must finally break 

 up and the corpuscles must disperse or re-arrange them- 

 selves after the ejection of some of their number. We are 

 thus led to conjecture that the several chemical elements 

 represent those different kinds of communities of corpuscles 

 which have proved by their stability to be successful in 

 the struggle for life. If this is so, it is almost impossible 

 to believe that the successful species have existed for all 

 time, and we must hold that they originated under con- 

 ditions about which I must forbear to follow .Sir Norman 

 Lockyer in speculating.' 



But if the elements were not eternal in the past, we 

 must ask whether there is reason to believe that they will 

 be eternal in the future. Now, although the conception 

 of the decay of an element and its spontaneous trans- 

 mutation into another element would have seemed abso- 

 lutely repugnant to the chemist until recently, yet analogy 

 with other moving systems seems to suggest that the 

 elements are not eternal. 



.\t any rate it is of interest to pursue to its end the 

 history of the model atom which has proved to be so 

 successful in imitating the properties of matter. The laws 

 which govern electricity in motion indicate that such an 

 atom must be radiating or losing energy, and therefore 

 a time must come when it will run down, as a clock does. 

 When this time comes it W'ill spontaneously transmute 

 itself into an element which needs less energy than was 

 required in the former state. Thomson conceives that an 

 atom might be constructed after his model so that its 

 decay should be verv slow. It might, he thinks, be made 

 to run for a million years, but it would not be eternal. 



Such a conclusion is an absolute contradiction to all 

 that was known of the elements until recently, for no 

 symptoms of decav are perceived, and the elements exist- 

 ing in the solar system must already have lasted for 

 millions of years. Nevertheless, there is good reason to 

 believe that in radium, and in other elements possessing 

 very complex atoms, we do actually observe that break-up 

 and spontaneous re-arrangement which constitute a trans- 

 mutation of elements. 



It is impossible as yet to sav how science w'ill solve 

 this difficulty, but future discovery in this field must surely 

 prove deeply interesting. It may well be that the train of 

 thought which I have sketched will ultimately profoundly 

 alifect the material side of human life, however remote it 

 may now seem from our experiences of dailv life. 



I have not as yet made any attempt to represent the 

 excessive minuteness of the corpuscles, of the existence 

 of which we are now so confident ; but, as an introduction 

 to what I have to speak of next, it is necessary to do 

 so. To obtain any adequate conception of their size we 

 must betake ourselves to a scheme of threefold magnifi- 

 cation. Lord Kelvin has shown that, if a drop of water 

 were magnified to the size of the earth, the molecules of 

 water would be of a size intermediate between that of a 

 cricket-ball and of a marble. Now each molecule contains 

 three atoms, tw-o being of hydrogen and one of oxygen. 

 The molecular system probably presents some sort of 

 analogy with that of a triple star ; the three atoms, re- 

 placing the stars, revolving about one another in some 

 sort of dance which cannot be exactly described. I doubt 

 whether it is possible to say how large a part of the space 

 occupied by tlie whole molecule is occupied by the atoms ; 

 but perhaps the atoms bear to the molecule some such 

 relationship as the molecule to the drop of w^ater referred 

 to. Finally, the corpuscles may stand to the atom in a 

 similar scale of magnitude. Accordingly a threefold 

 magnification would be needed to bring these ultimate 

 parts of the atom within the range of our ordinary scales 

 of measurement. 



I have already considered what would be observed under 

 ■*he triply powerful microscope, and must no>v return to 

 1 " Inorganic Evolution." (Macmill.-in, 1900. 



NO. 1868, VOL. 72] 



the intermediate stage of magnification, in which we con- 

 sider those communities of atoms which form molecules. 

 This is the field of research of the chemist. Although 

 prudence would tell me that it would be w-iser not to speak 

 of a subject of which I know so little, yet I cannot refrain 

 from saying a few words. 



The community of atoms in water has been compared 

 with a triple star, but there are others known to the 

 chemist in which the atoms are to be counted by fifties 

 and hundreds, so that they resemble constellations. 



I conceive that here again we meet with conditions 

 similar to those which we have supposed to exist in the 

 atom. Communities of atoms are called chemical com- 

 binations, and we know that they possess every degree of 

 stabilitv. The existence of some is so precarious that the 

 chemist in his laboratory can barely retain them for a 

 moment ; others are so stubborn that he can barely break 

 them up. In this case dissociation, and re-union into new- 

 forms of communities are in incessant and spontaneous 

 progress throughout the w'orld. The more persistent or 

 more stable combinations succeed in their struggle for 

 life, and are found in vast quantities, as in the cases cf 

 common salt and of the combinations of silicon. But no 

 one has ever found a mine of gun-cotton, because it ha^ 

 so slight a pow-er of resistance. If, through some acci- 

 dental collocation of elements, a single molecule of gun- 

 cotton were formed, it would have but a short life. 



Stability is, further, a property of relationship to 

 surrounding conditions ; it denotes adaptation to environ- 

 ment. Thus salt is adapted to the struggle for existence 

 on the earth, but it cannot withstand the severer conditions 

 which exist in the sun. 



SECTION A. 



MATiIEM.>\TICS AND PHYSICS. 



Opening Address by Prof. A. R. Forsyth, Sc.D., LL.D., 



M.ATH.D., F.R.S., President of the Section. 

 • According to an established and unchallenged custom, 

 our proceedings are inaugurated by an address from the 

 President. Let me begin it by discharging a duty which, 

 unhappily, is of regular recurrence. If your President only 

 mentions names when he records the personal losses 

 suflfered during the year by the sciences of the Section, the 

 corporate sense of the Section will be able to appreciate 

 the losses with a deeper reality than can be conveyed by 

 mere words. 



In Mr. Ronald Hudson, who was one of our secretaries 

 at the Cambridge meeting a year ago, we have lost a 

 mathematician whose youthful promise had ripened into 

 early performance. The original work which he had 

 accomplished is sufficient, both in quality and in amount, 

 to show that much has been given, and that much more 

 could have been expected. His alert and bright personality 

 suggested that many happy years lay before him. All 

 these fair hopes were shattered in a moment by an accident 

 upon a Welsh hillside ; and his friends, who were many, 

 deplore his too early death at the age of twenty-eight. 



The death of Mr. Frank McClean has robbed astronomy 

 of one of its most patient workers and actively creative 

 investigators. I wish that my own knowledge could enable 

 me to give some not inadequate exposition of his services 

 to the science which he loved so well. He was a man of 

 great generosity w'hich was wise, discriminating, and more 

 than modest ; to wide interests in science he united wnde 

 interests in the fine arts. Your Astronomer Royal, in the 

 Royal Observatory at Cape Town, will not lightly forget 

 his gift of a great telescope ; and the L'niversity of Cam- 

 bridge, the grateful recipient of his munificent endowment 

 of the Isaac Newton Studentships fifteen years ago, and 

 of his no less munificent bequest of manuscripts, early 

 printed books, and objects of art, has done what she can 

 towards perpetuating his memory for future generations 

 by including his name in the list, that is annually recited 

 in solemn service, of her benefactors who have departed 

 this life. 



In the early days of our gatherings, when the set of 

 cognate sciences with which we specially are concerned 

 had not yet diverged so widely from one another alike in 

 subject and in method, this inaugurating address was 

 ■characterised bv a brevitv that a President can envv and 



