G.—ENGINEERING 155 
£14 per kw., and this is recalculated for each load factor, the station 
wages and maintenance also being adjusted. ‘The curve is much flatter, 
and from 0-5 downwards its costs are lower than the pit-head station. 
Although at unity load factor the cost per kw. is £50, this reduces to 
£23 at 0-3 and to £18-5 at o-21 load factor. 
The stations of the Galloway scheme are to be mostly of this type, 
but the costs, when analysed in this way, are considerably larger, in 
fact 50 per cent. larger. The estimates given by the promoters in the 
parliamentary inquiry bring out the cost per kw. at £27 at a load 
factor of 0-21, at which it was proposed the stations should work, and 
the cost per unit on the above basis of calculation comes up to 0 +34 pence, 
which is also the figure estimated by the promoters. The pit-head 
figure is 0°32 pence, so that in its own area and for peak loads there is 
little difference, though with higher load factors the pit-head station 
rapidly gains. ‘The neighbourhood is, however, quite unable to absorb 
the 100,000 kw., which it is proposed to develop, on peak load or even 
as acomplete load. It has been suggested that power can be transmitted 
to Carlisle, which is 50 miles away, and this, as will be shown below, 
will add 0-022 pence to the cost, if the load factor is 0-21. This brings 
the total to 0-36 pence, nearly the cost for a normal steam station. As 
Carlisle has a coalfield on each side of it, the advantage of the trans- 
mitted power becomes rather illusory, and the grid will not be greatly 
helped by the scheme, except in Galloway and Wigtownshire. 
It might be imagined that with cost curves of different shape a happy 
apportionment of loads would yield a lower combined cost. It will be 
found, however, that little difference is made if the average load factor 
is not below 0-4, for the steam station curves are becoming flatter, and 
the reduction in their cost is absorbed by the higher cost of the peak 
load station. Each case must be worked out for itself, as no general 
rule can be given, and there are too many variables to allow of a 
mathematical determination of the conditions for a minumum cost, but 
in most cases the effect is disappointing, and the more so the higher the 
load factor of the system. 
Cost oF ‘TRANSMISSION. 
The position of generating stations brings in the cost of transmission. 
In the coal areas the numerous sources of supply will on the whole reduce 
transmission costs, but the supply of power to outside areas depends 
chiefly on the cost of electric transmission, as compared with other 
methods. 
The cost of long-distance transmission of electric energy has been 
much reduced by increased voltage, and by reduced cost of transformers 
and transforming substations. It is considerably influenced by load 
factor, for capital charges and wages are constant, while line losses are 
much reduced on low load factors. For any distance of importance the 
grid at 132,000 volts will be the usual means, and the cost of transmission 
Over 100 miles is shown in Fig. 2 for the various generating stations, the 
difference being caused by the respective costs of the power wasted in 
the line. The conditions assumed are—interest at 3? per cent., repayment 
in thirty years, and annual upkeep at £20 per mile, which makes a total 
