546 



SCIENCE 



[N. S. Vol. XXXIV. No. 878 



mechanics of the universe. The influence 

 of atomic compressibilities may be per- 

 ceived everywhere, and in most cases each 

 fact seems to fit easily and without con- 

 straint into its place in the hypothesis. 

 Even apparent exceptions, such as the ab- 

 normal bulk of ice, may be ascribed in a 

 reasonable fashion to superposed effects. 

 A detailed discussion of many applications 

 of the theory is impossible here, but a few 

 may be suggested, in order to make clearer 

 its possibilities. 



The satisfying of each valence of an 

 atom would cause a depression on the 

 atomic surface, owing to the pressure ex- 

 erted by the affinity in that spot. The 

 stronger the affinity, the greater should be 

 this distortion. Evidently this conception 

 gives a new picture of the asymmetric car- 

 bon atom, which, combined with four other 

 different atoms, would have upon its sur- 

 face depressions of four unequal magni- 

 tudes, and be twisted into an unsymmet- 

 rical tetrahedron. The combining atoms 

 would be held on the faces of the tetra- 

 hedron thus formed, instead of impossibly 

 perching upon the several peaks. Accord- 

 ing to this hypothesis, the carbon atom 

 need not be imagined as a tetrahedron in 

 the first place; it would assume the tetra- 

 hedral shape when combined with the other 

 four atoms. One can easily imagine that 

 the development of each new valence would 

 change the affinities previously exercised, 

 somewhat as a second depression in the side 

 of a rubber ball will modify a forcibly 

 caused dimple in some other part. Thus a 

 part of the effect which each new atom has 

 on the affinities of the other atoms already 

 present may be explained. 



Many other physico-chemical phenomena 

 assume a new aspect when viewed from the 

 standpoint of this idea. New notions of 

 the mechanism of the critical phenomena, 

 surface tension, ductility, malleability, ten- 



acity and coefficient of expansion are 

 gained. The peculiar relations of material 

 and light, such as magnetic rotation, fluo- 

 rescence, partial absorption, and so forth, 

 may be referred to the modified vibrations 

 of distorted atoms. The deviations from 

 the exact fulfilment of many older general- 

 izations concerning volume (such as the 

 equation of van der Waals already cited, 

 the comparative volumes of aqueous solu- 

 tions, especially of electrolytically disso- 

 ciated substances,^^ and the variations in 

 the crystal forms of isomorphous sub- 

 stances) are seen to be a foregone conclu- 

 sion. Moreover, the theory, although not 

 necessarily dependent on the modern belief 

 that atoms are built up of numbers of much 

 smaller corpuscles, is consistent with that 

 belief, for would not such an entity be 

 compressible ? 



The more closely the actual data are 

 studied, the more plausible the hypothesis 

 of compressible atoms appears. Ten years' 

 experience with its interpretations leads me 

 to feel that the idea is highly suggestive 

 and helpful in stimulating new search after 

 truth and in correlating and codifying di- 

 verse facts. By such fruit are hypotheses 

 justified. 



The relation between heat of reaction 

 and change of volume stimulates interest 

 in chemical thermodynamics and curiosity 

 as to the mechanism of the output of en- 

 ergy during chemical change. A search 

 for accurate data wherewith to reason 

 about this question soon revealed the un- 

 certain nature of many of the figures. 

 Here, in the domain of thermochemistry, 

 as in those of atomic weights and compres- 

 sibilities, new methods were needed in 

 order to attain precise results. Aceord- 



'' Baxter has very recently discussed this matter 

 from the point of view of the theory of compres- 

 sible atoms {J. Amer. Chem. Soc, 1911, 33, p. 

 922). 



