10* Mr. H. TomlinHon. The Influence of [June 19, 



experiments on moduli of elasticity and electrical conductivity 

 described in Parts I and II of this paper* was determined in the 

 following manner : The wires, which had been previously well 

 annealed, were wound round a steel rod and so made into coils of 

 length about 2 inches, inner diameter \ inch, and outer diameter 1| 

 inches, the rod was then withdrawn and the coil inserted into a thin 

 brass envelope. The envelope consisted of a hollow cylinder 2 inches 

 in length and 2 inches in diameter, terminated at both ends by a trun- 

 cated cone. One of the conical ends was closed and could be unscrewed 

 so as to receive the coil of wire, and was, after the insertion of the 

 coil, screwed on again. At the other extremity of the envelope was 

 an aperture \ inch in diameter, through which a thermometer could 

 be inserted, so that its bulb would lie along the axis and in the centre 

 of the coil of wire. The brass envelope and the contained coil were 

 heated in an air-chamber consisting of two concentric copper 

 cylinders of equal length connected at their two ends, so as to enclose 

 between them a layer of water \ inch thick. The length of the air- 

 chamber thus formed was 14 inches, and the inner diameter 2J inches, 

 so that the envelope could freely slide through the chamber. The 

 two ends of the air-chamber, which was placed in a horizontal 

 position, were closed by corks, through the centre of one of which 

 passed a thermometer, and through a very small hole in the centre of 

 the other was drawn a fine but strong thread attached with one 

 extremity to the envelope, and with the other wound round a little 

 piece of wood which prevented the thread from being' dragged 

 through the hole when the former was drawn tight. The envelope 

 and contained wire were heated before immersion in the water of the 

 calorimeter in one set of experiments to about 60 C., and in another 

 set to about 100 C. The envelope served a double purpose, as it not 

 only enabled compensation to be made for loss of heat during the 

 transference of the wire from the air-chamber to the calorimeter, but 

 also was of use in distributing the heat uniformly throughout the 

 coil. 



Preliminary observations were made for the purpose of ascertaining 

 the rise of temperature which would be caused by immersing the 

 heated envelope only in the water of the calorimeter. 



Every precaution was taken both with regard to the instrument 

 themselves and the mode of using them to avoid error, and the 

 formulae given below may be received with great confidence. 



It will be seen that the thermal capacity of all the metal 

 examined increased with the temperature, a result which we fine 

 confirmed by the observations of other investigators. 



The thermal capacities of the alloys platinum-silver, and Gerr 

 silver are, within the limits of error, exactly the same as the 

 * " Phil. Trans.," Part I, 1883, p. 1. 



