On the Nature of Liquids. 129 



resistance of the larger primary coil was not much more than 

 one fifteen-hundredth of the whole resistance in circuit with it 

 — the ratio of the resistances was no doubt somewhat disturbed 

 by the unequal heating of the two primary circuits, and was 

 in reality rather less than what was inferred from the marked 

 values of the coils used. That this was the case was shown 

 by the fact that the apparent ratio decreased progressively 

 from 40*3 to 39*45, as the strengh of the testing current was 

 diminished from its first value to rather less than one sixth. 

 A better arrangement of the apparatus would have been to 

 put the two primary wires in series with the battery, and to 

 have connected the two secondaries in parallel circuit ; but 

 the matter was not thought important enough to require a 

 repetition of the measurements. 



The method of measuring coefficients of mutual induction 

 described in this paper may perhaps be of use in the experi- 

 mental study of dynamo-electric machines, whose whole action 

 depends upon the variation of the coefficient of mutual induc- 

 tion between the field-magnet coils and the armature coils, as 

 the latter take various positions during the course of a 

 revolution. 



XV. On the Nature of Liquids, as shown by a Study of the 

 Thermal Properties of Stable and Dissociable Bodies. By 

 William Ramsay, Ph.D., and Sydney Young, D.Sc* 



THE fundamental concept of Chemistry, as well as of 

 Physics, is the molecular and atomic constitution of 

 matter. This concept serves to represent to the chemist the 

 definite composition of compounds, and, to some degree, the 

 nature of isomerism, while all attempts to realize and explain 

 the progress of chemical change depend on its adoption. 

 This concept also furnishes to the physicist the means of 

 conceiving the relations of heat, light, magnetism and elec- 

 tricity to matter ; and where the action of one of these agents 

 involves not merely a change in the form, but also in the 

 nature of the matter, the problem becomes of deep interest 

 to both chemist and physicist. The action of heat on matter, 

 from the physical side, involves an increased molecular 

 motion, tending to separate individual molecules from each 

 other, on the one hand ; or, on the other, if this separation be 

 opposed by confining walls, to increase the momentum and 

 number of impacts on those walls, and therefore to raise the 

 pressure. But this increased molecular motion is accom- 



* Communicated by the Physical Society : read December 11, 1886. 



