CHARACTER OF THE CURRENT — UNIPOLARITY — EFFECT OF HEAT. 161 



after showing that similar phenomena can take place with good conductors, proves 

 that with soap, &c. many of the effects are the mere consequences of the bodies 

 evolved by electrolytic action. 



1636. I conclude, therefore, that i\ie facts upon which the doctrine of unipolarity 

 was founded are not adverse to that unity and indivisibility of character which I 

 have stated the current to possess, any more than the phenomena of the pile itself, 

 which might well bear comparison with those of unipolar bodies, are opposed to it. 

 Probably the effects which have been called effects of unipolarity, and the peculiar 

 differences of the positive and negative surface when discharging into air, gases, or 

 other dielectrics (1480. 1525.) which have been already referred to, may have con- 

 siderable relation to each other*. 



. 1637. M. DE LA Rive has recently described a peculiar and remarkable effect of 

 heat on a current when passing between electrodes and a fluid-}-. It is, that if pla- 

 tina electrodes dip into acidulated water no change is produced in the passing cur- 

 rent by making the positive electrode hotter or colder ; whereas making the negative 

 electrode hotter increased the deflexion of a galvanometer affected by the current, 

 from 12° to 30° and even 45°, whilst making it colder diminished the current in the 

 same high proportions. 



1638. That one electrode should have this striking relation to heat whilst the other 

 remained absolutely without, seem to me as incompatible with what I conceived to be 

 the character of a current as unipolarity (1627. 1635.), and it was therefore with some 

 anxiety that I repeated the experiment. The electrodes which I used were of platina ; 

 the electrolyte, water containing about one sixth of sulphuric acid by weight : the 

 voltaic battery consisted of two pairs of amalgamated zinc and platina plates in dilute 

 sulphuric acid, and the galvanometer in the circuit was one with two needles, and 

 gave when the arrangement was complete a deflexion of 10° or 12°. 



1639. Under these circumstances heating either electrode increased the current ; 

 beating both produced still more effect. When both were heated, if either were 

 cooled, the effect on the current fell in proportion. The proportion of effect due to 

 heating this or that electrode varied, but on the whole heating the negative seemed 

 to favour the passage of the current somewhat more than heating the positive. 



regret I confess I have not access, and cannot do justice, to the many most valuable papers in experimental elec- 

 tricity published in that language. I take this opportunity also of stating another circumstance which occasions 

 me great trouble, and, as I find by experience, may make me seemingly regardless of the labours of others : — it 

 is a gradual loss of memory for some years past; and now, often when I read a memoir, I remember that I have 

 seen it before, and would have rejoiced if at the right time I could have recollected and referred to it in the 

 progress of my own papers, — M. F. 



* See also Hare in Silliman's Journal, 1833. xxiv. 246. 



t Bibliothfeque Universelle, 1837. vii. 388. 

 MDCCCXXXVIII. Y 



