[E] Schweigger’s Jahrbuch de Chimie, &c. 1830.  Heft 8.  Not understanding German, it is with extreme regret I confess I have not access, and cannot do justice, to the many most valuable papers in experimental electricity 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.

1636.  I conclude, therefore, that the 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 considerable relation to each other[A].

  [A] See also Hare in Silliman’s Journal, 1833. xxiv. 246.

* * * * *

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[A].  It is, that if platina electrodes dip into acidulated water, no change is produced in the passing current 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 deg. to 30 deg. and even 45 deg., whilst making it colder diminished the current in the same high proportions.

  [A] Bibliotheque Universelle, 1837, vii. 388.

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 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 deg. or 12 deg..

1639.  Under these circumstances heating either electrode increased the current; heating 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.  Whether the application of heat were by a flame applied underneath, or one directed by a blowpipe from above, or by a hot iron or coal, the effect was the same.