on the preservation of the copper sheathing of ships, &c. 245 
and perhaps the rapidity of the motion of the ship ; ) circum- 
stances in relation to which I am about to make decisive 
experiments. 
Many singular facts have occurred in the course of these 
researches. I shall mention some of them, that I have con- 
firmed by repeated experiments, and which have connections 
with general science. 
Weak solutions of salt act strongly upon copper ; strong 
ones, as brine, do not affect it ; and the reason seems to be, 
that they contain little or no atmospheric air, the oxygene of 
which seems necessary to give the electro-positive principle 
of change to menstrua of this class. 
I had anticipated the result of this experiment, and upon 
the same principle of some others. 
Alkaline solutions, for instance, impede or prevent the 
action of sea water on copper ; having in themselves the 
positive electrical energy, which renders the copper negative. 
Lime water even, in this way, renders null the power of 
action of copper on sea water.* 
The tendency of electrical and chemical action being 
always to produce an equilibrium in the electrical powers, 
the agency of all combinations formed of metals and fluids 
is to occasion decompositions, in such an order that alkaline, 
metallic, and inflammable matters are determined to the 
negative part of the combination, and chlorine, iodine, oxy- 
gene and acid matters to the positive part. I have shown in 
the Bakerian Lecture for 1806 , that this holds good in the 
Voltaic battery. The same law applies to these feebler 
* I am at present engaged in applying this principle to experiments on the pre- 
servation of animal and vegetable substances. 
