4 8ir W. Thomson on the Thermoelastic, Thermomagnetic } 



sphere, will keep the top of the tube sufficiently moist for an 

 immense time. 



The only possible changes which can go on in this cell are 

 in the zinc and the solution in immediate contact with it. 

 This solution can at any time be drawn off with a pipette and 

 replaced by fresh, without greatly affecting the liquid in the 

 bottle (if the cork be air-tight) ; and the zinc can still more 

 easily be taken out and replaced by a new piece. 



I have described the cell as at present made ; but if there 

 were any chance of its coming into use as a standard, a few 

 modifications might be introduced. Thus the zinc might be 

 a short rod with an india-rubber collar fitting the tube and 

 with a short copper wire attached to it, which should project 

 above the cork instead of the zinc, the joint being a little way 

 down the tube and protected by a coat of varnish from damp 

 air. A set of experiments would have to be made to determine 

 the dependence of electromotive force on temperature ; and 

 then a thermometer with a short scale might be fixed in each 

 cork. 



University College, London. 



IJ. Ov the Thermoelastic, Thermomagnetic, and Pyroelectric 

 Properties of Matter. By William Thomson, M.A., late 

 Fellow of St. Peter's College, Cambridge, Professor of Na- 

 tural Philosophy in the University of Glasgow *. 



1. A BODY which is either emitting heat, or altering its 



-£*- dimensions against resisting forces, is doing work upon 



matter external to it. The mechanical effect of this work in 



* [This paper is in the main a reprint from an article which appeared 

 under the title " On the Thermo elastic and Thermomagnetic Properties 

 of Matter, Part I.," in April 1855, in the first number of the ' Quarterly 

 Journal of Mathematics,' hut which was confined to the thermoelastic 

 part of the subject. The continuation, in which it was intended to 

 make a similar application of thermodynamic principles to magnetic in- 

 duction, was never published or written ; but the results which it should 

 have contained were sufficiently indicated in a short article on "Thermo- 

 magnetism," which I wrote at the request of my friend and colleague the 

 late Professor J. P. Nichol for the second edition of his 'Cyclopaedia,' 

 published in 1860, and which I include in the present reprint. The 

 addition of " Pyro-Electricity," which I now make to the title of the 

 former article, is justified by another short quotation from the second 

 edition of Nichol's ' Cyclopaedia' (article " Thermo-Electricity, Divi- 

 sion I.— Pyro-Electricity, or Thermo-Electricity of Nonconducting Crys- 

 tals "), and a short addition, now written and published for the first time, 

 in which the same thermodynamic principles are applied to this form of 

 th erm oelectric action . 



Several additions both in the shape of text and footnote are appended 

 in the course of the reprint. These are all distinguished by being en- 

 closed in brackets, [ ].] 



