96 Mr. C. V. Burton on the " Dimensions " of 



A more suitable core for the helix than indiarubber is the 

 flexible gas-tubing made of plaited and varnished canvas. It 

 is very uniform in cross section; and by withdrawing the 

 metal spiral upon which it is woven and mounting it on a 

 spindle in a screw-cutting lathe, it is easy to wind the wire 

 uniformly upon it. 



The use of the lathe is the more desirable, as measurements 

 of potential by the helix depend very much for their accuracy 

 upon the uniformity with which it is wound ; this being espe- 

 cially the case if its position in the field does not happen to 

 coincide with the direction of the lines of force. 



To keep the turns in place the small spaces between them 

 may be filled with soft cotton- thread. 



University College, Bristol. 



X. On the u Dimensions " of Temperature in Lengthy Mass, 

 and Time; and on an Absolute C. G.S. Unit of Temperature. 

 By Charles V. Burton, B.Sc. (Lond.).* 



SIR W. THOMSON'S second absolute scale gives us the 

 means of finding the ratio between two temperatures, 

 independently of any arbitrary convention as to the size of 

 degrees. We are therefore bound to consider temperature as 

 a physical quantity capable of exact measurement. Now every 

 such quantity has certain dimensions in length, mass, and 

 time ; and I here propose to find the dimensions of tem- 

 perature. 



Let temperatures be represented on Sir W. Thomson's 

 absolute scale, so that nothing remains arbitrary except the 

 size of the degrees. Consider an absolutely perfect gas whose 

 temperature on this scale = t. Let the mean kinetic energy 

 of a molecule of the gas = E. Then we have 



E=fo, (1) 



where h is the same for all temperatures and for all perfect 

 gases ; being independent of the mass per molecule of the 

 gas, and determined solely by the size of the degrees on our 

 scale of temperature. 



If we write (1) in the form 



t= l ■ ■ w 



we see that a temperature (t) is completely determined by the 

 average-kinetic-energy-per-molecule (E) of a perfect gas 



* Communicated by the Author. 



