S2 C. G. Gmeliii’s Observations on the Prodiictlon of 
are two specimens of painting, probably of Indian origin. The 
one appears to be a savage, with something like a bow in his 
hand, and furnishes the hint, that it was done when that instru- 
ment of death was in use. The other is so much defaced, that 
it is impossible to say what it was intended to represent. 
Art. V. — Observations mi the Production of Electricity by Cmi- 
tact. By C. G. Gmelin, Professor of Chemistry in the Uni- 
versity of Tubingen. Communicated by the Author. 
Sir Humphry Davy, in his treatise on the chemical effects 
of electricity, published, in the year 1806, some experiments, 
which, in a very simple and unequivocal manner, seemed to 
prove the electrical opposition between Alkalies and Acids, — an 
opposition well established by the action of galvanic electricity 
upon the combination of alkalies and acids. He discovered, that 
acids which may be exhibited in a dry state, such as Oxalic^ 
Succinic^ Benzoic^ Boracic^ Phosphoric acid, having the form 
of crystals, or that of a powder, if’ touched on an extensive sur- 
face, with a copper-plate, insulated by a glass handle, were ne- 
gatively electrified, while the copper-plate was positively elec- 
trified; and that, on the contrary, alkalies and earths, as Lime^ 
Strontia, Magnesia^ were positively electrified, while the copper 
was negatively electrified. Zinc and tin, when tried instead of 
copper, produced the same effect. The intensity of the posi- 
tive charge of the metal, appeared to be the same, whether the 
acid was insulated by glass, or in communication with the earth. 
I must own, that several reasons induced me to put some dis- 
trust in the justness of the conclusions drawn from the above 
experiments. 
1. Because Sir H. Davy himself has found, that if the tem- 
perature changed a little, as for instance, if the earths were touch- 
ed during their cooling, the opposite state of electricity often 
appeared. 
2. Because in those experiments the Condenser was employed, 
an instrument, which may so easily be a source of ermrs, and 
which at any rate unnecessarily prolongs the experiment. 
