At the close of 1906 the population of Australia was approximately 4,120,000, exclusive of aborigines.
A solution of the free acid may be obtained by decomposing the barium salt with dilute sulphuric acid and concentrating the solution in vacuo until it attains a density of about 1.35 (approximately), further concentration leading to its decomposition into sulphur dioxide and sulphuric acid.
It is then placed in a tank of water and kept at a certain fixed temperature, usually 75° F., until it assumes approximately a constant electrical state.
The length paid out and the rate of paying out are obtained approximately from the number of turns made by the drum P and its rate of turning.
One of the longest circuits upon which it has been successfully worked is that between St Petersburg and Omsk, a distance of approximately 2400 miles of iron wire, with three repeating stations.