234 



SCIENCE. 



[N. S. Vol. XXII. No. obi 



whether it is possible to say how large a 

 part of the space occupied by the whole 

 molecule is occupied by the atoms ; but per- 

 haps the atoms bear to the molecule some 

 such relationship as the molecule to the 

 drop of water referred to. Finally, the 

 corpuscles may stand to the atom in a sim- 

 ilar 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 the triply powerful micro- 

 scope, and must now return to the inter- 

 mediate stage of magnification, in which 

 we consider those communities of atoms 

 which form molecules. This is the field of 

 research of the chemist. Although pru- 

 dence would tell me that it would be wiser, 

 not to speak of a subject of which I know 

 so little, yet I can not 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 constella- 

 tions. 



I conceive that here again we meet with 

 conditions similar to those which we have 

 supposed to exist in the atom. Communi- 

 ties of atoms are called chemical combina- 

 tions, and we know that they possess every 

 degree of stability. 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 disso- 

 ciation and reunion into new forms of com- 

 munities are in incessant and spontaneous 

 progress throughout the world. The more 

 persistent or more stable combinations suc- 

 ceed in their struggle for life, and are 

 found in vast quantities, as in the cases of 



common salt and of the combinations of 

 silicon. But no one has ever found a mine 

 of guncotton, because it has so slight a 

 power of resistance. If, through some 

 accidental collocation of elements, a single 

 molecule of guncotton were formed, it 

 would have but a short life. 



Stability is, further, a property of rela- 

 tionship to surrounding conditions ; it de- 

 notes adaptation to environment. Thus 

 salt is adapted to the struggle for existence 

 on the earth, but it can not withstand the 

 severer conditions which exist in the sun. 



G. H. Darwin. 



Ujstiveesity of Cambridge. 



[The president here announced that he 

 proposed to consider various theories of 

 evolution in the heavens in the second por- 

 tion of his address, to be delivered at 

 Johannesburg on Wednesday, August 30.] 



ADBRESH TO THE MATHEMATICAL AND 

 PHYSICAL SECTION OF THE BRITISH 

 ASSOCIATION FOB THE ADVANCE- 

 MENT OP SCIENCE.^ 



According to an established and unchal- 

 lenged custom, our proceedings are inaugu- 

 rated 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 suffered dur- 

 ing 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 



^ South Africa, 1905. 



