LXVI. E. K. SCOTT. 
high pressure; (c) unfavourable atmospheric conditions, 
sea air and dust. Sixty thousand volts is the highest 
pressure at present in use, and it has been found that with 
the wires 63 feet apart the discharge losses can be kept 
down to areasonable amount. It isnow proposed, however, 
to employ 100,000 volts, and the Muskegan Power Co. of 
Michigan are changing over one of their lines. 
The highest voltages at present employed in Australasia 
are 23,000 volts at Hillgrove to 35,000 volts at Dunedin, 
but except on the coastline belt almost any pressure could 
be used, because the airissodry. Deciding upona voltage 
and periodicity is almost as important as deciding upon a 
railway gauge, and it would be well to have such matters 
settled. 
Size of Wire.—The size of wire depends partly on how 
many hours each day it carries the maximum load ; if only 
a few hours the voltage drop at full load can be say 15% 
otherwise 10% is the rule. The actual size employed 
is generally just about i inch diameter, if of solid copper, 
and about 2 if of stranded aluminium. The latter metal is 
preferred for long lines because it is cheaper. Thus for 
equal conductivity 48 lbs. aluminium is equal to 100 lbs. of 
copper, so that if aluminium is being sold in the standard 
form at say £100 u ton (in ingot it is £80) then copper wire 
must be £48 (in ingots it is about £55 at the present time) 
in order to compete. Of course aluminium presents a 
ereater surface to the wind and for ice and snow to form 
upon, but these are not difficulties likely to be met with in 
Australia as they are in Canada and some parts of Hurope. 
It should be noted that when branch lines have to carry 
small currents the size of a copper or aluminium conductor 
would be too small mechanically, say below No. 4 8.W.G., 
and in such cases iron wire is frequently used. 
