270 The N.Z. Journal of Science and Technology. [Jan. 
We see from the figures in the accompanying table that heat obtained 
directly from coal or indirectly from gas and coke involves about the same 
initial destruction of coal. In the latter case, however, there are valuable 
by-products. Moreover, future gas practice may be expected to become 
more efficient. 
We next come to the consideration of how far our hydro-electric resources 
will influence the problem. The total developable water-power in the 
Dominion is probably of the order of 3,000,000* continuous horse-power,, 
or 6,000,00 horse-power on a 50-per-cent, load factor. Moreover, there are 
possibilities of power-generation from the various thermal regions. At 
present, however, electric power is developed in New Zealand equivalent 
to only about horse-power per head, and the basis of the Government’s 
scheme is only J horse-power per head of population.*)* This latter figure 
means, for example, the provision of one ordinary three-bulb radiator 
continuously running for each family of five persons, with no power left 
over. Thus there is little hope of hyro-electricity providing in the imme¬ 
diate future more than a fraction of the Dominion’s fuel necessities. 
We are thus in a position of possessing limited supplies of coal and 
electricity, and the question arises as to how to make the best use of these 
limited quantities. We have seen that electricity is transformed into power 
with 85 per cent, efficiency of transformation. We have also shown that 
coal is transformed into heat with over ten times the efficiency of its trans¬ 
formation into power in fairly small plants. Further, lighting by electricity 
is more economical than lighting by gas. It thus follows that our hydro¬ 
electric resources should first of all be used for power and light, and the 
surplus, if any, used for cooking. Our coal should be used for heating, 
either directly or through the medium of gas and coke.J Hydro-electricity 
should, therefore, as it becomes available, be used for lighting for factories 
and for power for suburban railways ; and in order that there may be a 
large surplus for domestic use its development should be expedited as much 
as possible. Assuming 5 lb. of coal per horse-power hour, it can be calculated 
that 60,000 continuous horse-power of hydro-electricity would, if wholly 
applied as power, take the place of over 1,000,000 tons of coal per year— 
nearly half the total amount used in New Zealand each year. 
In conclusion, we wish to thank Mr. L. Birks, B.Sc., Chief Electrical 
Engineer to the Public Works Department, for suggesting the problem, 
and the New Zealand Institute for transmitting to us a research grant from 
the Government to meet the expenses in connection with the investigation. 
* New Zealand Official Year-book , 1914, p. 657, where estimates are given of all 
sources of power over 1,000 horse-power. 
f Public Works Statement, N.Z. Parliamentary Paper D.-l , 1920. 
j A further extension of this argument indicates that even at present we should 
conserve our coal until such time as it is more valuable owing to shortage, and use 
imported coal. 
