THOMAS ROOKE, XCVILI. 
The reason why these areas are not much larger is not 
due to any electrical difficulty but to the density of the 
demand which has to be met, andin all these schemes 
electricity will be transmitted through underground cables 
which cost a great deal more than the overhead lines used 
in America, and necessary where the demand is scattered. 
In America, development of territory is being carried out 
on a much larger scale than elsewhere, and electrical lines 
‘distribute power for this purpose. The areas to be covered 
are very great, and compare in this respect with Australia. 
The longest transmission lines are to be found in California 
and are being operated by the Bay Counties’ Power Co. 
and the Standard Electric Company. Power houses have 
been erected at Colgate and EHlectra, and electricity is 
transmitted over a distance of 211 miles to San Francisco, 
or 140,000 square miles of territory are within reach ofa 
single power house, and even longer and larger transmiss- 
ions are contemplated. From twenty-two such stations 
transmission lines could be extended over an erea equal to 
the whole of Australia. At Colgate and neighbouring 
power houses 25,000 HP. is developed. At EKlectra the 
Standard Company have 15,000 HP. and are now adding 
21,000 HP. Thesystem on which these power transmissions 
are operated is as follows:—The generators supply elec- 
tricity at 2,300 volts to static transformers which step up 
to 40- 50- or 60,000 volts. The transformers are grouped 
and delta connected on the low tension side. The high 
tension windings are star connected, the centre of the star 
being earthed. The insulation of each conductor has there- 
fore to withstand a normal H.M.F. not exceeding 35,000 
volts to earth. The poles are of cedar from 25 to 60 feet 
in height, the insulators are of brown glazed porcelain hav- 
ing a very large surface. These are supported on wooden 
pins and wooden cross arms. The weight of overhead con- 
7—July 20, 1908. 
