might, as to the matter, very properly have appeared in this volume, but
they would have interfered with it as a simple reprint of the "Experimental
Researches" of the Philosophical Transactions.

Then I wish to refer, in relation to the Fourth Series on a new law of
Electric Conduction, to Franklin's experiments on the non-conduction of
ice, which have been very properly separated and set forth by Professor
Bache (Journal of the Franklin Institute, 1836. xvii. 183.). These, which I
did not at all remember as to the extent of the effect, though they in no
way anticipate the expression of the law I state as to the general effect
of liquefaction on electrolytes, still should never be forgotten when
speaking of that law as applicable to the case of water.

There are two papers which I am anxious to refer to, as corrections or
criticisms of parts of the Experimental Researches. The first of these is
one by Jacobi (Philosophical Magazine, 1838. xiii. 401.), relative to the
possible production of a spark on completing the junction of the two metals
of a single pair of plates (915.). It is an excellent paper, and though I
have not repeated the experiments, the description of them convinces me
that I must have been in error. The second is by that excellent
philosopher, Marianini (Memoria della Societa Italiana di Modena, xxi.
205), and is a critical and experimental examination of Series viii, and of
the question whether metallic contact is or is not _productive_ of a part
of the electricity of the voltaic pile. I see no reason as yet to alter the
opinion I have given; but the paper is so very valuable, comes to the
question so directly, and the point itself is of such great importance,
that I intend at the first opportunity renewing the inquiry, and, if I can,
rendering the proofs either on the one side or the other undeniable to all.

Other parts of these researches have received the honour of critical