/ / 3 £~ 
1918.] The N.Z. Journal of Science and Technology. 21 
for pasteurizing, scalding, and washing. For separating and churning, the * 
steadiness and uniformity of speed are of great advantage as compared 
with the steam-engine. For milking-machines the ease of starting" and 
stopping, and the unattended operation of the motors, as well as the 
cheapness of the power as compared with petrol and kerosene fuel, deter¬ 
mine the matter without question, and are making quite a revolution in 
dairying matters wherever the mains are accessible. A most striking 
development has been the success of the Tai Tapu Dairy Company. This 
company buys power in bulk for operating its butter-factory in Tai Tapu, 
and also reticulates the district for retail distribution to its suppliers and 
consumers within its district. There are now fourteen miles of 3,000-volt 
and six miles of low-tension line, supplying seventy-six consumers, includ¬ 
ing twenty-five milking-machines. The financial results have been very 
satisfactory to all parties—the farmer, the dairy company, and the Depart¬ 
ment ; production has been stimulated, and one of the comforts of the 
city has been carried out to the hardworking dairy-farmer. 
Quarries and Brickyards .—Two large quarries, three large brickyards, 
and one pottery are now driven by Lake Coleridge power, and others are 
waiting for a supply. In these cases the large instantaneous overload 
capacity of the electric motor is of the utmost value. It is found in nearly 
every case that the former engines were very much overpowered for their 
average work, owing to the necessity of their carrying an occasional over¬ 
load without stopping, which the electric motor does without difficulty. 
Hospitals and Institutions .-—There are now six hospitals and similar 
institutions supplied from the mains, in most cases on the maximum- 
demand system, at £1 per month per kilowatt of maximum demand. This 
enables them to utilize the energy for a wide range of purposes with the 
highest economy. If used for lighting only, for an average of, say, 1,000 
hours per year, it works out at under 3d. per unit. But up to the lighting- 
capacity the energy can be used on this scale at other hours of the day at 
no additional cost. It is thus available for heating, cooking, refrigerating, 
pumping, milking, shearing, chaff-cutting, sawing, sewing, and ironing and 
other laundry-work. Between 10 p.m. and 9 a.m. it is used for hot-water 
heating, at no additional cost. At Sunnyside Hospital, by combining all 
these operations and keeping a graphical record of the demand by means 
of a curve-drawing watt-meter, the energy is obtained for all purposes at 
a rate below two-thirds of a penny, which still yields to the Department 
a satisfactory return of £1 per month per kilowatt of maximum demand. 
Economy of Coal in Canterbury. 
Another aspect of this subject is economy in the use of coal in Canter¬ 
bury as the result of the operation of the Lake Coleridge plant. This is of 
particular importance just now as a measure of national efficiency, owing 
to the demand or man-power for the prosecution of the war and for 
essential industries. 
The coal-consumption in the most efficient and well-designed steam 
plant in Canterbury—the tramway power-station—for the last complete 
year of coal-firing was about 8,800 tons to generate 5,179,457 units with 
a normal maximum load of about 1,200 kilowatts, or 1,600 horse-power-— 
that is, over 5 tons per horse-power year, working on about a 50-per-cent, 
load-factor. The ordinary small commercial steam plant consumes from 
three to five times as much coal as this, though as its load-factor is low— 
usually 10 per cent, to 20 per cent.—the owner does not, as a rule, realize 
how much coal per actual horse-power hour it is using. It is found in 
