RECENT ADVANCES IN SCIENCE 211 



9 cms., while in theory the lighter N atom ought to have a range 

 about 19 per cent, greater than the O atom. This would 

 be accounted for if the energy of impact was shared between an 

 H atom and the remaining part of the disrupted N atom. 



No doubt the conclusion of this paper will be subjected to 

 searching criticism before long — there are many obvious gaps 

 in the experimental work to be filled. It is, however, a reason- 

 able assumption that Prof. Rutherford will, by dint of his own 

 energy and the enthusiasm he evokes among his pupils, soon be 

 engaged in filling the lacunae. His imagination has already 

 suggested the feasibility of searching for a still more intense 

 projectile than the a particle from radium C, wherewith to 

 disintegrate the structure of other light atoms. 



PHYSICAL CHEMISTRY. By Prof. W. C McC. Lewis, M.A.. 

 D.Sc, University, Liverpool. 



Latent Heat of Fusion. — The process of fusion of a solid has 

 been investigated by Honda {Science Reports, Tohoku Univer- 

 sity, September 191 8) from the point of view of the quantum 

 hypothesis. The chief interest of the work lies in the view 

 taken of the nature of the molecular and atomic movement in 

 the liquid or fused state of a substance. Our long familiarity 

 with the principle of the continuity of the gaseous and liquid 

 states, and the important results gained in this field, have 

 served to impress physicists and chemists with the close 

 analogy which exists between a liquid and a gas. On the 

 basis of Honda's considerations, we are led to expect a far 

 closer analogy between a solid and a liquid, in so far as the 

 type of molecular or atomic energy is concerned. Let us take 

 the simple case of a monatomic solid. Its energy consists of 

 vibration of the atoms. On the equipartition view this energy 

 amounts to 3 RT per. gram-atom, of which one-half is kinetic, 

 one-half potential energy. On the quantum theory this ex- 

 pression is modified in the sense that T itself is replaced by 

 a complex expression (involving T), which allows for the fact 

 that the heat capacity diminishes as the temperature falls. 

 In both cases we restrict ourselves to vibrational movement 

 of the atoms alone ; we do not consider any other possible 

 mode of motion. According to Honda, however, the mole- 

 cules or atoms may possess small dependent rotational vibra- 

 tions about their centres of mass, and when we approach the 



