I have not tried the effect of electro-depositing platinum upon 
it as a means of roughening the surface of platinum foil; but 
experiments with clean platinum in sulphuric acid, and with 
ciean platinum in strong solution of caustic potash, and again 
with iron-wire gauze, and even with iron-wire gauze spread with 
fine iron-filings, in the latter liquid, as supports for the layer of 
dioxide, sufficiently evinced that mechanical roughness alone is 
quite unproductive of the close intimacy of contact between the 
peroxide and the metal plate required to establish the necessary 
kind of rheomotive continuity between them. But on the other 
hand, if iron in caustic potash could by any means be brought 
superficially (perhaps by kilning it in oxide of manganese) to as inti- 
mate conjunction during the charging process with lead peroxide, as 
platinum-foil is brought by a preparatory coking of its surface, 
it would be an equally effective and equally indestructible substi- 
tute for a lead plate with platinum, and as far as I have observed 
it, as retentive an accumulator of the charge communicated to it 
as platinum itself is either in dilute acid or in caustic potash. 
But on an iron conductor in a solution of caustic alkali, 
dioxide of lead itself must be originally spread out; since this 
liquid seems incapable (at least without protracted action), 
although it soon forms the spongy-lead layer opposite to it, of 
converting the minium into a dioxide layer. The electrolysis of 
water by iron electrodes in a solution of caustic soda and of 
caustic potash, also, is singularly rapid, attended perhaps by a 
minimum counter-force of polarisation, and by little production 
of ozone, so that the proportion of oxygen absorbed to the oxygen 
wasted and given off in charging,! unless a weak current only is 
applied, is less than with dilute sulphuric acid, and the liquid 
has an inconvenient tendency to froth up. But in regard to 
storage and retention of a charge communicated to it, and in its 
manner of furnishing the return or secondary current, this 
arrangement appears to be just as efficacious as one with a clean 
platinam conductor. 
A cell made with minium laid on two clean platinum-leaves 
of a pair of ordinary pint Grove-cells, weighed when placed with 
acid in its glass jar (not much larger than a glove’s thumb- or finger- 
stall), just seven ounces, Yet when well charged it rang a call- 
bell continuously for eight hours, When afterwards re-charged, 
and washed, and left to dry unavoidably for a fortnight, on 
simply immersing it then in a solution of caustic potash, it rang 
a bell with a few intervals of intermittence of the current, for 
twenty hours before it was exhausted. It still continues with 
similar intermittences of a few day’s rest to furnish residual bell- 
ringing currents of two or three hours’ duration each, sufficiently 
proving the extreme hardiness and retentiveness of its construc- 
tion. A rather bulkier cell formed with two coated sheets of 
iron-wire gauze in caustic potash comported itself in an exactly 
similar manner, having just now, five days after being charged, 
and without yet ceasing its clatter, rung a bell continuously for 
thirty-six hours.? 
But between these small messenger-currents and the substantial 
stream that can be drawn from a properly-formed Planté or 
Faure cell with lead-plates of the same size, there is as much 
difference as between a caged song-bird and a slipped falcon ; and it 
has afforded me extreme pleasure to be able to reproduce success- 
fully the normal action of the lead accumulators with an inde- 
structible metal plate as the negative conductor, by the fortunate 
possession and trial of a piece of platinum-foil roughened in the 
way described above, wnich was accidentally preserved from 
some former experiments on mossy incrustations produced 
on platinum surfaces by contact with carbon or with heated 
vapours in a carbonising kiln. 
Although already convinced of its correctness by these experi- 
ments, I owed to the pages (pp. 382-83) of Prof, Silvanus 
Thompson's excellent book of ‘‘ Elementary Lessons in Elec- 
tricity and Magnetism” which treat of secondary batteries, my 
first acquaintance with the general acceptance as an established 
fact of the view that gaseous polarisation of the plates by oxygen 
and hydrogen is in these extreme, as muchas in ordinary weaker 
cases, the source of the secondary or return current ina secondary 
cell—that, for example, in Plante’s cells the lead-plates acquire 
their high tension by ‘‘ becoming with use coated with a semi- 
porous film of brown dioxide of lead, presenting a large amount 
of surface and holding the gases well”; and that by Faure’s 
* See Drs. Gladstone and Tribe’s experiments and remarks on the relative 
absorptions and losses of the eclectrolysed gases in charging a lead-cell ; 
“The Chemistry of the Planté and Faure Accumulators,” Part IT. ; 
NATURE, xxv. p. 462. 
* This cell’s current lasted forty hours ; but a week later a residual current 
‘ftwo more hours’ duration wos extracted from it. 
NATURE 
method of preparation, the improvement is effected that ‘cells 
thus prepared sooner acquire the effective spongy brown surface 
of dioxide of lead.” 
It is, in fact, a well-known result, and one which I can 
thoroughly confirm from the tests and observations to which I 
have submitted it, that whatever electromotive force the simple 
contact of dioxide of lead by itself may be sufficiently energetic 
to produce,’ it is to a natural aptitude which it possesses besides 
for occluding ozone or nascent electrolytic oxygen in its pores, 
and probably also by undergoing at the same time chemical 
superoxydation, to which its remarkably high tension and effec- 
tive electromotive deportment in secondary cells must really be 
ascribed. It is thus that a platinum cathode, by occluding 
electrolytic hydrogen in its substance, becomes electropositive, 
and that palladium similarly charged to repletion with hydrogen 
by electrolysis, even becomes at last spontaneously inflammable, 
In Dr. Gore’s treatise in the ‘‘ Circle of the Sciences” on 
“*Electro-Deposition,” it is mentioned (pp. 55, 56) that in rapid 
negative depositions of antimony, the freshly-deposited metal is 
explosive to such a degree, with evolution of heat and of a cloud 
of white vapour at points where it is rubbed, that thickly plated 
articles are sometimes liable to sudden fractures and destruction 
by this accident, if incautiously handled, even for some hours 
after they are washed and dried. Either the storage of nascent 
hydrogen in the antimony, it is supposed, or of an unstable mole- 
cular form of antimony itself, is here effected also by the gal- 
vanic current; and ozone is a form of oxygen which is only 
producible by similar means of exciting and provoking molecular 
accumulation or storage of energy. 
The absorbed oxygen’s state in the peroxide film would seem to 
be, as that of occluded hydrogen has appeared to be in metals, 
one of easy dissociation from, joined and consorted to physical 
admixture with, sorne precarious chemical oxide or compound 
depending, as it seems reasonable to suppose, for its existence in 
some degree upon the quantity of its free materials present in 
the substance with it. But the freedom with which the gases are 
able to diffuse themselves everywhere through the film or metal, 
is no doubt a sufficient and suitably adequate condition to main- 
tain the precarious compound’s chemical integrity, so as to make 
it a retentive source of energy, as long as the uncombined gas- 
portions with which it is surrounded in the film or metal, are not 
withdrawn from it by a galvanic discharge arising from comple- 
tion either of the secondary circuit or else of some unavoidable 
channels of destructive local actions. 
The contact theory of current excitation requires such close 
linkage together of circuit elements, for the establishment of a 
current through them, that if the highly negative peroxide film 
should be severed by liquid, or by any substance equally inert to 
a liquid in the voltaic chain, from its metal plate conductor, its 
effective electromotive force would immediately disappear from 
the circuit. This is the ground on which I surmised the need, 
above, of such a perfect contact between the peroxide film and 
its metal carrier that only a molecular union produced between 
them in the charging process could well be expected to prevent 
the intrusion of the liquid of the cell, to the current’s detriment, 
between the actively electromotive gas-absorbing layer and its 
adjoining inoperative metal-plate conductor, or battery-con- 
nection. 
It is, again, to the hints contained in a paragraph on a later 
page (p. 391) of Prof. Silvanus Thompson's book, describing 
the phenomena and the modes of producing Nobili’s rings, that 
I owe the suggestion of trying the experiment of iron-gauze 
electrodes in solution of caustic alkalies, which produced a very 
satisfactory form of secondary cell, showing at least a possibility 
of perhaps effecting in it some future practical improvements, 
A. S, HERSCHEL 
College of Physical Science, Newcastle-on-Tyne, March 20 
Aristotle on the Heart 
ALLOW me space to say, in reference to Dr. Richardson’s 
letter in NATURE, vol. xxv. p. 505, that my note on Aristotle’s 
account of the heart, though so lately published, was written 
many years ago, and therefore in complete independence of Prof. 
Huxley’s article on the same subject. This fact, of course, in 
no way lessens Prof, Huxley’s complete rights of priority ; but I 
* This was shown by F. Munck, in Poggendorff's Annalen (circa, 1835), to 
surpass negatively that of all the other metallic oxides, not excepting the 
black oxide of manganese, by means of the usual contact experiments with 
a gold-leaf electroscope and condenser. 
[April 6, 1882 
