350 Chronicles of Science. | April, 
workable as gutta-percha. It readily softens when plunged in boiling 
water, is soluble in turpentine and chloroform, receives and retains 
impressions permanently, and is adapted for seals to documents. 
These specimens are sent in response to premiums offered by the 
Society of Arts for the discovery of a substitute for gutta-percha. 
A curious fact has been mentioned by Mr. James Napier* in refer- 
ence to the dynamics of the galvanic battery, which is somewhat in 
opposition to the polar theory with mutual transfer of elements, advo- 
cated by Professor Williamson. Suppose a vessel divided by a porous 
diaphragm has dissolved in each division an equal quantity of sulphate 
of copper, and into each of the divisions is placed a plate of copper 
attached to the poles of the battery which completes the circuit; now, 
by the polar theory there should be a mutual transfer of the acid and 
copper between the two divisions, so that at any time, if the current of 
electricity were stopped, the solution in the two divisions would be the 
same as when the experiment began. But in reality this is not the 
case, the copper dissolved in the division attached to the zine end of 
the battery will be deposited as metal on the copper plate in that divi- 
sion, while the acid element will be transferred to the other division. 
But the copper in that other division will not pass through the dia- 
phragm in the opposite direction to the acid, so that ultimately the one 
division will have neither copper nor acid in solution, whilst the other 
division (that connected with the copper end of the battery) will have 
double the quantity of sulphate of copper in solution that it had at the 
commencement. 
The electrical properties of pyroxiline paper and gun cotton have 
long been known to be very great, but it has only lately been pointed 
out by Professors Johnstone and Silliman that these azotized species 
of cellulose are the most remarkable negative electrics yet observed ; 
upon friction with these, sulphur, hitherto the most highly negative 
electric known, becomes positive. 
We have to thank Mr. Nassau Jocelyn, of the British Legation, 
Turin, for drawing our attention to a novel voltaic arrangement devised 
by Professor Minotti, of that city, which, though essentially based upon 
Daniell’s principle, is said to be far more constant and powerful than 
any other arrangement of that rheomotor. It consists simply of a 
copper disc placed at the bottom of a glass vessel having a gutta-percha- 
covered wire soldered to its rim, which issues from the top of the 
vessel and forms the positive electrode. Over the copper is laid a 
layer of powdered sulphate of copper, and over this a stratum of coarse 
sand, or—what has been found to answer better—a stratum one inch 
in thickness of common glass beads, such as are used for working 
purses, and may be purchased at a cheap rate at the workshops. On 
this layer lies a solid cast-cylinder of zinc, from whence proceeds the 
negative pole of the element. On the cell being filled with common 
spring water, so as to cover the zinc, the battery begins to work, and will 
keep constant and uniform for seven or eight months. The intensity of 
* «Philosophical Magazine,’ vol. xxvii. p. 52. 
+ ‘Silliman’s Journal,’ January, 1864. 
