286 



The Rev. Canon Moseley on the 



[Feb. 2, 



order to determine the capacity of the sliding condenser at the lower extre- 

 mity of its range, a spherical condenser, so constructed that its capacity 

 could be accurately determined in absolute measure, was employed. An 

 apparent discrepancy in the results obtained, arising from an inequality in 

 the condensers forming the platymeter, is then considered, and the method 

 of deducing the true result investigated. A series of experiments is then 

 described which gave 1*975 as the specific inductive capacity of paraffine, 

 that of air being taken as unity, but failed to show whether this alters with 

 variations of temperature. An improved form of condenser, composed of 

 concentric brass cylinders with paraffine for the dielectric, and the results 

 obtained from it, are then described. The measurements made at different 

 temperatures show no variation of specific inductive capacity. In order to 

 allow to the paraffine freedom of expansion with temperature, another 

 form of condenser was employed, and the same results obtained. A series 

 of experiments was then made on the expansion of paraffine with tempera- 

 ture, in order to estimate the effect of this upon the capacity of paraffine 

 condensers. As a mean of the results, it was found that the linear expan- 

 sion of paraffine at 9° C. is '000237 per degree. Some further measure- 

 ments of the cylindrical condenser were made with the same result as 

 before. Thus all the measurements of this condenser made at temperatures 

 ranging from — 12°* 15 to 24-35 C. show no variation of specific inductive 

 capacity of paraffine with temperature. This was found to be I' 977, that 

 of air being taken as unity. 



In a note added to the paper a description is given of an improved form 

 of sliding condenser. 



III. "On the Uniform Flow of a Liquid." By Henry Moseley, 

 M.A., D.C.L., Canon of Bristol, F.R.S., and Corresponding 

 Member of the Institute of France. Received December 1, 

 1870. 



(Abstract.) 



The resistance of every molecule of a liquid at rest which a solid (by 

 moving through it) disturbs, contributes its share to the resistance which 

 the solid experiences ; so that the inertia of each molecule so disturbed and 

 its shear must be taken into account in the aggregate, which represents the 

 resistance the liquid offers to the motion of the solid. The motions com- 

 municated to the molecules of a liquid by a solid passing through it, and 

 the resistances opposed to them, however, are so various, and so difficult to 

 be represented mathematically, that in the present state of our knowledge 

 of hydrodynamics the problem of the resistance of a liquid at rest to a 

 solid in motion is perhaps to be considered insoluble. As it regards the 

 opposite problem of the resistance of a solid at rest to a liquid in motion 

 (as in the case of a liquid conveyed through a pipe), there are in like 

 manner to be taken into account the disturbances created by that re- 



