472 
NATURE 
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[April 17, 187 | 
 . 
borealis on the evenings of April. 1 and 2. On April 1 
it was first noticed at 84 4go™) when an intense auroral 
glow pervaded the N. sky and gave an effect similar to moon- | 
rise. At851™a broad streamer became visible, reaching a 
height of 11°. This streamer was situated 2° N. of B Cassiopeiz, 
and appeared to be connected with an auroral arch under Cassi- 
opeia, running from N.W. to N. On the following evening, 
April 2, the auroral light was again intense in due N. 
THE additions to the Zoological Society’s Gardens during the 
last week include a Bacha Eagle (.Spilornis bacha) from Malacca, 
presented by Mr. W. Jamrach; a Madagascar Porphyrio 
(Porphyrio Madagascariensis) from Madagascar, presented by 
Miss Furlonger ; a Cuttle-fish (Octopus vulgaris) presented by 
the Brighton Aquarium Co.; a great grey Shrike (Lanius 
excubitor) presented by Mr. Hawkins; a Crested Pelican 
(Pelecanus crispus) from S, Europe, presented by Dr. Doyle; 
a Vulpine Phalanger (P/ialangista vulpina) ; a great Kangaroo 
(Macropus giganteus) ; a yellow-footed rock kangaroo (Petrogale 
xanthopus) ;and some Tibetan Wolves (Camis daniger) born in 
the Gardens ; two Hunting Crows (Cissa venatoria) from India ; 
a Cocoi Heron (Ardea cocot) from the W. Indies; a Broad- 
banded Armadillo (Xexurus unicinctus) from Brazil ; two Rock 
Whiting ; a Whiting Pout, two Lump-fish, and six Bream all 
purchased. 
‘THis battery is founded on a reaction, brought by the 
authors before the Royal Society} last spring, in which it 
was shown that if pieces of copper and silver, in contact, were 
immersed in copper nitrate solution in presence of oxygen, a 
deposit of cuprous oxide took place on the silver plate with a 
corresponding solution of the copper plate, resulting from the 
decomposition of the copper nitrate in the manner shown in the 
following formulz :— 
Before contact is made 
mAg | O | Cu2NO, | Cu2NO, | nCu 
After contact 
mAg | Cu,O | Cu2NO, | Cu2NO, | (n-2)Cu 
It is evident that this action is continuous until either the 
copper or the oxygen is exhausted. 
It was stated in that paper, that a galvanic current passed 
through the solution from the copper to the silver, and also that 
this was only one case of a large class of similar reactions. 
The battery takes the form of a shallow circular vessel con- 
taining the solution, and the plates are arranged horizontally, the 
silver plate being at the surface. It will be apparent on glancing 
at the above equations, that the combination of the oxygen only 
takes place in the neighbourhood of the silver; hence it was 
evidently desirable to increase as much as possible the proximity 
of the silver plate to the air, and also the surface exposed by the 
silver. This was accomplished as shown in the adjoining 
sketch. The silver has the; form of a shallow tray, full of 
crystals of silver, and perforated to allow the circulation of the 
copper solution. The tray is arranged so that the crystals 
should just rise above the surface, and being, of course, always 
wet, they very much increase the absorbing surface of the liquid, 
* Abstract of paper read at the Royal Society, Thursday, April 3, by 
J. H. Gladstone, Ph.D., F.R.S., and Alfred Tribe, F.R.S. 
t Proc. Roy. Soc, vol. 20, p. 290. 
The whole arrangement is put upon a wooden stand, and the 
plates are attached to two uprights fixed in the stand. 
The strength of the copper nitrate solution is 6 percent. This 
gives about the maximum of effect ; a 24 percent solution gives _ 
only half the current; and a 30 per cent solution gives two- 
thirds, A solution stronger than 6 per cent. is also apt to pro- 
duce a deposit of subnitrate instead of suboxide. : 
The best proportionate areas of the silver and copper-plates 
was investigated in two series of experiments, in one of which 
the silver remained the same, while the copper surface was 
diminished by varnishing, and in the other set the copper remained 
the same while the silver was diminished. The following table 
gives the results in the latter case. 
of a Thomson’s galyanometer :— 
The deflections are those 
Ss 
Proportion of Surfaces. Deflection. 
Copper Silver. Expt. 1 | Expt. 2. Expt, 3. 
1 
I 0°25 = — 7 
I o'5 — — 16"0 
I 0°75 — _ 21°0 
I ro aoe 32° 28°90 
I 1°33 4r 40° = 
I 2'0 56° 54° —_— 
I 4/0 96° 92° — 
It thus appears that an increase in area of the silver plates 
causes a proportionate increase in the current. It was also 
found that heat greatly increases the activity of this cell, a cell 
giving a deflection of 40 at 20° C., gave one of 250 at 50°C. ; 
and the increase in the higher degrees of this range of tempe- 
rature was much greater than in the lower. 
From the nature of the reaction it might be expected that the 
current would gradually diminish on account of the using up of 
the oxygen in the neighbourhood of the silver. Such a dimi- 
nution always does take place at first—agitating the liquid 
ought, under these circumstances, to increase the action, It 
does so, ’ : 
It might also be expected that upon breaking contact for some 
time, so as to allow oxygen to diffuse itself from other parts of | 
the solution, the current upon again making contact would be as 
strong, or nearly so, as before. This also was found to be 
the case. 
An experiment was made by putting a cell, with plates con- 
nected by a wire, under a bell-jar full of air over mercury. It 
was expected that the mercury would rise inside the jar from 
absorption of the oxygen. The mercury did rise, and the 
oxygen was so completely removed that a lighted taper was im- 
mediately extinguished in the remaining gas. The apparatus 
used in this experiment was exhibited to the Royal Society. 
Comparative experiments were made with aérated and des 
aérated copper nitrate slution, It was found that the amount 
of action ia the latter case was little or nothing, and what small 4 
action there was was clearly attributable to the difficulty of com- 
pletely excluding air. | 
Two experiments were made alike in all respects, except that — 
in one case the cell used was filled with a solution simply de- 
prived of oxygen, while the other cell was filled with a soluion 
through which a current of C O, was passed for sometime. The 
first was placed in the air, and gave a deflection of 110 rising to 
115, but the second was placed in a vessel full of carbonic acid 
gas, and gave a deflection of 20, which gradually fell to 3. H 
It was proved experimentally that the cuprous oxide deposited 
on the silver was compensated by an equivalent soluiion of the 
copper plate. The cuprous oxide is sometimes deposited in 
crystals visible to the naked eye, and shown by a lens to be __ 
regular octahedra, | 
One cell having plates two inches in diameter was found suffis 
cient to decompose such metallic salts as the nitrates of copper, 
silver, and lead, platinum being used for the negative electrode, 
and for the positive the same metal as existed in the salt experi- 
mented on. Six cells were sufficient to decompose dilute sul- 
phuric acid and dilute hydrochloric acid pretty quickly, copper 
electrodes being employed. 
The theoretical interest of this battery lies in the fact that it 
differs from all other galvanic arrangements, inasmuch as the 
binary compound in solution is incapable of being decomposed 
