Electricity can travel in either direction through a wire.
Electricity from a power station constantly alternates from one direction to the other and this is referred to as Alternating Current electricity. When A.C. electricity has travelled once in both directions that is called a 'cycle'. The number of cycles per second is referred to as the frequency. All rain is weekly acidic due to the fact that carbon dioxide dissolves in water in the atmosphere producing carbonic acid. The burning of coal and oil produces Carbon oxides but also Nitrogen and Sulphur oxides.