M. A. F. Sundell on Galvanic Induction. 283 



for while the gas adheres strongly to such bodies, the water has 

 a much weaker adhesion. Hence, while such bodies are not 

 wetted by the water, they are so by the gas ; and consequently 

 in a supersaturated gaseous solution their surfaces become 

 covered with bubbles, which increase in size, loosen their hold, 

 and ascend, while other bubbles are formed in their place. This 

 action goes on until the solution loses its state of supersatura- 

 tion and becomes saturated only; but in this condition the 

 bodies in this class remained covered with the bubbles last 

 formed upon them, and that for days together. The solu- 

 tion, however, can be restored to its state of supersaturation 

 by diminishing the pressure or by increasing the temperature, 

 in which case the liberation of bubbles from the surfaces is 

 renewed. 



It may here be remarked that bodies in class I. are said to be 

 "dirty" or "active," or "dynamic" or "nuclear," or " uncatha- 

 rized " when they are contaminated, however slightly, with any 

 one of the bodies in class II. 



The third, and by far the most numerous class, contains 

 bodies that are distinguished by porosity — such as various kinds 

 of wood and the charcoals made from them, and a large variety 

 of other bodies, including some of the metals. But as the con- 

 sideration of this, as well as of the fourth class, which includes 

 soluble substances, involves a number of details, we must defer 

 them to another occasion. 



Highgate, N. 

 March 15, 18/3. 



XXXVII. On Galvanic Induction. By A. F. Sundell*. 



ALTHOUGH many natural philosophers have turned their 

 attention to the phenomena of galvanic induction and 

 endeavoured to deduce them from a common principle, yet very 

 few experiments have been made in order to ascertain if the 

 theories agree in all respects with experience. The object of 

 the experiments hitherto made has been, for the most part, to 

 find in what manner the induction depends on the form and 

 magnitude of the circuits and the strength of the primary cur- 

 rent. Recently Professor Edlund in Stockholm has made these 

 phenomena the subject of a theoretical research f, and shown 

 that they, like all known electrical phenomena, have their origin 

 in the luminiferous sether. He has also deduced a formula for 



* Communicated by the Author. 



f *' Sur la Nature de l'Electricite," Archives des Sciences de la Biblio- 

 theque Universelle (Geneve), 1872, Mars et Avril j Philosophical Magazine, 

 1872, vol. xliv. pp. 81 asd 174. 



