308 Dr. G. Gore on Changes of Temperature caused 



the surfaces of mutual contact of two different substances (or 

 of two masses of the same substance in different physical or 

 molecular states) are usually localities of change and trans- 

 ference of energy. Two such substances can rarely be brought 

 into mutual contact without such change occurring, and the 

 changes which occur are more or less different in every differ- 

 ent case. In multitudes of cases the changes are of a chemical 

 character, in others they are physical. Yolta showed that the 

 mere contact of two different metals rendered them electro- 

 polar. Many years ago Pouillet {Annates de Chemie, 1822, 

 vol. xx. pp. 141-162), also Regnault (Gmelin's c Handbook 

 of Chemistry,' vol. i. p. 300), and recently Meissner ('Nature, 5 

 Nov. 4, 1886, p. 24), found that when finely divided dry solid 

 substances, such as silica, metals, emery, carbon, &c. were 

 wetted by liquids, such as water, benzol, or alcohol, which 

 have no dissolving or corrosive action upon them, heat is 

 evolved. Pouillet employed many oxidizable substances. 

 Daniell states that when a liquid begins to flow through a dry 

 tube, heat is evolved ('Text-book of Physics,' p. 284). 



In the present research I have endeavoured to extend our 

 knowledge of the thermal phenomena of this subject. The 

 following is a sectional sketch and a description of the appa- 

 ratus and method of experimenting. 

 A is a glass vessel usually containing 

 50 centim. of the liquid and the bulb 

 of a sensitive thermometer, and is 

 supported in a wire ring having three 

 slender legs. B is a wide glass tube 

 containing 100 grains of finely pre- 

 cipitated pure and dry silica or other 

 fine powder. C is a narrow glass 

 tube open at both ends, and loosely 

 enclosing the stem of the thermo- 

 meter ; it is supported firmly at its 

 upper end by the clip D, and has 

 fixed securely upon its lower end a 

 conical and very smooth piece of 

 cork which accurately fits the outer 

 tube. 



Both the glass vessels A and B 

 are thickly coated with cotton wool. 



The thermometer is capable of di- 

 stinctly indicating a one-hundredth 

 of a Centigrade degree change of 

 temperature, and its bulb is sup- 

 ported a quarter of an inch above 

 the bottom by a small piece of cork. 



