48 REPORT—1846. 
~ 
element, two pairs; and while it took sixteen cells of the water battery to produce a 
_ given effect on the electroscope, ten of the same cells when charged with dilute acid 
produced the same effect in the same instrument. 
The static effects of a voltaic battery are very feebly developed, except when the 
battery is insulated, and the difficulties of insulation in an extended series are at all 
times great. In the battery excited by acid solutions these difficulties are much in- 
creased, in consequence of the conducting power of the liquids ; still they are not 
insurmountable; and as of all the batteries hitherto constructed, the nitric acid battery 
of Grove is composed of elements of the highest chemical affinity, the 13 in. 
author determined on constructing one, in which the effects of tension 
should be heightened to the extent of exhibiting the spark before the 
circuit was completed, which he hoped to accomplish without being 
compelled to extend the series to any extraordinary number, as he had 
done in the water battery previously described. 
For this purpose he had 100 glass cells constructed three inches deep, 
with stems seven inches long; the zinc of each series was attached to 
a slip of platinum foil; each cell was carefully charged in the usual 
manner (but only half-full), with strong nitric and dilute sulphuric 
acid, and great care was taken that the outside of each cell with the 
stem was perfectly dry. To the terminals of this battery were attached 
the copper plates of the micrometer electrometer described in a former 
paper (Phil. Trans. 1840). On approximating the plates of this in- 
strument to about 555th of an inch, a series of minute sparks took 
place, and in a few seconds the usual voltaic are was produced ; this arc 
could then be elongated to the extent of half an inch, in consequence of 
the particles of the copper having passed between the plates. 
If, in lieu of the copper plates, pieces of charcoal be similarly ap- 
proximated to z2,5ths of an inch, the arc is at once produced, instead 
of the sparks as from the discs ; the loose particles of the carbon being 
more easily detached by the force of tension, and consequently at once 
producing the are. 
The author believes that this is the first instance in which a ¢rue spark 
has been obtained from so small a series of the voltaic battery. 
‘soul ¢ 
‘soqouy £ 
On the Decomposition of Water into its constituent Gases by Heat. 
By W. R. Grove, F.R.S. 
Mr. Grove called attention in the first place to the fact, proved by Cavendish 
and the French philosophers, that oxygen and hydrogen being exposed to a high’ 
temperature the electric spark immediately combined to form water. He stated his 
belief that the explosion of the mixed gases by the electric spark was due only to the 
heat of the spark, and not to any specific electrical effect. He then announced his 
discovery that similar processes to those by which water may be formed are capable 
of decomposing water. Priestley’s method for decomposing gases by passing them 
through heated tubes was described, and the advantages of using a form of eudio- 
meter devised by Mr. Grove, in which an incandescent platina wire was employed 
to effect combination and decomposition, were pointed out. By an apparatus of this 
kind, ammonia, camphor, the protoxide and peroxide of nitrogen were readily de- 
composed. It was stated that hydrogen gas exposed to the ignited wire always 
showed the presence of oxygen, and that it is impossible to pass hydrogen gas 
through water without its taking up so much oxygen as to acquire the power of 
giving luminosity to phosphorus in the dark. 
It was found that if equal volumes of hydrogen and carbonic acid were exposed to 
the action of the ignited wire, there was a contraction to one volume, leaving a resi- 
due of carbonic oxide. If carbonic oxide alone was exposed to the wire over water, 
the gas expanded in volume, and the carbonic oxide, taking oxygen from the water, 
was converted into carbonic acid. Here we have two dissimilar results produced by 
the same cause. By means of hydrogen we take oxygen from carbonic acid, leaving 
carbonic oxide ; and by means of carbonic oxide we take oxygen from water, leaving 
hydrogen. If steam is formed in the eudiometric tube and acted on by the ignited 
