378 The N.Z. Journal of Science and Technology. [Nov. 
The Larderello Natural Steam-power Plant, by Ugo Funaioli, Engineering , 
vol. 105, pp. 507, 508, 567, 568, 569, May 10 and 24, 1918. 
Near Yolterra, in Tuscany, over an area of about 100 square kilo¬ 
metres (38-61 square miles) a group of sqffioni (stream springs) and lagoni 
(boiling pools) exists which has been for many years the base of a 
flourishing chemical industry. The steam contains boric acid, ammonia, 
carbonic acid, sulphuretted hydrogen, nitrogen, and a small quantity 
of helium, and works exist for the production of boric acid, borax, 
and ammonium carbonate from the steam. As the region is rich 
in iron and copper pyrites, and the important steel centre of Piombino, 
and the cities Leghorn, Siena, and Volterra are near, the power ques¬ 
tion is important. Therefore, after successful experiments from 1897 
onward, the natural steam being used in piston engines without in¬ 
convenience, in 1912 a 330-horse-power turbo-generator was installed, 
and in 1916 a turbine power-station of 10,000 horse-power. The 
natural steam would probably drive the turbines without any hurtful 
amount of corrosion occurring, but the presence of the gases mentioned 
above would make the condensing plant and air-pumps of excessive 
size and cost, so pure steam is generated in evaporators. These are 
virtually vertical water-tube boilers with aluminium tubes, giving steam 
at 7J lb. pressure, which is superheated by the natural steam before passing 
through the turbines. As the natural sojjioni are not usually sufficiently 
productive of steam, 16 in. bores lined with iron tubes are put down a 
depth of 200-400 ft., which deliver up to 30,000 lb. of steam per hour at 
30-40 lb. pressure and at a superheated temperature of 180° C. Electricity 
is generated at 4,000 volts, stepped up to 36,000 volts for transmission. 
The power-lines radiate to Leghorn, Siena, Piombino, Massa, as well as 
to various local works and to Volterra. At different points they connect 
in parallel with the water-power systems of Terni and Ligure Toscana, 
and the lignite system of the Societa Mineraria del Yaldarno. The low- 
temperature steam system, entailing massive turbines and enormous 
condensing-towers and air-pumps, could hardly compete with ordinary 
power-stations, but the scarcity of coal in Italy, and the fact that the 
chemical industry is a by-product, so to speak, of the power-supply, alter 
the aspect of affairs. At Lago, in the same region, the natural steam is 
much freer from accompanying gases, and experiments are being carried 
on there to use the natural steam direct in the turbines, with the aid of 
a new type of separator for freeing the steam of gas. This will cut out 
the costly boilers, with the accompanying thermal loss and increased 
consumption of steam per horse-power-hour, thus both decreasing the 
capacity of the condensers and allowing the less expensive jet type to 
be used, and generally diminishing greatly the whole cost of the plant. 
Studies are also being made for the utilization of volcanic energy near 
Naples, at the famous solfatara of Pozzuoli. 
(These experiments are interesting to New-Zealanders because of the 
much more extensive and active thermal region of Rotorua. The question 
of adequate power may at once be granted, but that of cost compared 
with water-power or a large coal-power plant at Huntly would need close 
examination. If natural steam superheated to 400°-500° F. could be 
obtained around Rotorua directly suitable for turbines, it would probably 
prove the cheapest source of power-supply for the North Island; but 
experiments and investigation are needed. Transmission advantages 
