28 Dr. Gr. Gore on a Method of Measuring 



heated, similar to those exhibited by the oxide of zinc. 

 Cylinders of lime, for example, when freshly ignited in the 

 oxyhydrogen flame, attain a momentary brilliancy and white- 

 ness which is not reached during any subsequent ignition. 



The extraordinary brightness of the magnesium flame also 

 is undoubtedly to be ascribed to a state of initial incan- 

 descence such as that which we have observed in zinc oxide. 

 W. H. Pickering* found the character of the light of burning 

 magnesium to be that corresponding to a temperature con- 

 siderably above 3000° C. Recent measurements of the actual 

 temperature of the flame, however, show that it is not above 

 1400° C. 



Other instances of abnormal incandescence of the metallic 

 oxides might be cited. At what temperatures the effect 

 occurs, and what its precise nature is in the case of the 

 various substances in which the phenomenon presents itself, 

 must be determined by further experiment. 



Physical Laboratory of Cornell University, 

 June 1891. 



III. A Method of Measuring Loss of Energy due to Chemical 

 Union 8fc. By Dr. G. Goke, F.R.SJ 



IN this research a number of pairs of electrolytic sub- 

 stances, in some cases acids and alkalies, were selected, 

 and the conditions of the experiments so arranged that the 

 relative mean amount of loss or gain of energy of each pair 

 of substances during their act of chemical nnion, mixture, or 

 mutual decomposition whilst in solution, might be measured 

 by means of a small voltaic couple and the null method of 

 balance, with the aid of a suitable thermoelectric pile (see Proc. 

 Birai. Phil. Soc. vol. iv. p. 130, < The Electrician/ 1884, 

 vol. xii. p. 414) and an astatic galvanometer having 100 ohms 

 resistance in its coils. The voltaic couple consisted of a suit- 

 able positive metal and platinum, and was lowered into and 

 raised out of the electrolyte by means of a rack and pinion. 

 The positive metals usually employed were aluminium, tin, 

 cadmium, zinc, and magnesium. A little improvement in the 

 thermopile was used in this research ; it consisted in passing 

 a stream of cold water through a pipe immersed in the cold 

 oil-bath and thus keeping it at a constant temperature. 



The following is an outline of the method : — 1st. Take a con- 



* Proc. Amer. Acad. Arts and Sci. 1880. 

 f Communicated by the Author. 



