JElecti'icity by Contact. 
touching it with the zinc plate ; and when ignited to a white 
heat, the acid evaporated in white acid vapours. 
Oxalic acid made the metal constantly positively electrified 
when crystallised ; and when in the form of a powder (hydrate 
of oxalic acid) the evolved electricity was very weak* 
I now tried several salts. 
Pure carbonate qf barytes imparted to the metal constantly^ 
and under all circumstances, an intense positive electricity. 
Carbonate of Soda fused, and still very hot, imparted to the 
metal a very intense negative electricity. When it had assumed 
the temperature of the atmosphere, the metal was sometimes 
positively, sometimes negatively electrified. 
I now allowed some crystallised carbonate of soda to effloresce 
perfectly. If it was touched in this state^ the metal was con- 
stantly positively electrified, when the salt and the metal had as- 
sumed the temperature of the atmosphere ; and even when the 
salt and the metal were of a higher temperature, the metal was 
commonly positively electrified, and in a few instances negatively. 
It appears, therefore, again, that the very same body, when 
only in a different state, may be positively or negatively electri*- 
fled, by its contact with metals. 
Ciystals of sulphate of potash^ ignited and powdered, impart- 
ed to the metal, Avhen still quite hot, a weak positive electricity ; 
but this was so much increased on cooling, that though the weather 
was very damp, the gold leaf touched the pile, after a few contacts. 
Sulphate qfSoda, when quite freed from its water of crystal- 
lisation by its exposure to a dry atmosphere, rendered the metal 
positively electrified. 
The general result of these experiments is therefore thisj that 
the electrical opposition between acids and bases, though so well 
established by other means^ cannot be deduced from the electri- 
cal relation between these bodies and metals. 
Art. VI. — On the Coral Islands qf the Pacific Ocean. — By Dr 
A. VON Chamisso 
HE low islands of the South Sea and Indian Ocean owe their 
origin principally to the operations of several species of coral. 
• Published in the Appendix to Kotzebue’s Voyage of Discovery into the 
South Sea and Beering’s Straits, vol. Hi. p. 331. 
