520 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1&23 



nia, and the roads are good, though winding. The volcanic nature 

 of this district is shown by stretches of arid soil, the presence of many 

 " soffioni " and " lagoni," and by the occurrence in their vicinity of 

 sulphur, crystals of calcium carbonate, with pseudomorphous growths 

 of gypsum, larderellite (ammonium borate), and sassolinite (ortho- 

 boric acid) . 



For industrial utilization the supply of steam from " soffioni " is 

 not sufficient, and hence bore holes, 16 inches in diameter and from 

 200 to 500 feet deep, are sunk and protected from caving by iron tub- 

 ing. The steam issues at an average pressure of 2 absolute atmos- 

 pheres, and at a temperature varying from 100° to 190° C, friction 

 against the walls of the bore causing much of the superheat. Eecent 

 drillings have released steam at a considerably higher pressure, and 

 in quantities up to 60,000 kilograms (59 tons) per hour. At Larde- 

 rello the actual available output is above 150,000 kilograms per hour 

 from 135 bore holes, and generally there is abundant evidence of 

 enormous untapped supplies. The steam, which Prof. K. Nasini has 

 shown to be radio-active, contains an average of 0.06 per cent of boric 

 acid, with a maximum of 0.1 per cent, and about 4 to 6 per cent by 

 weight of gases, mainly carbon dioxide (over 90 per cent), but also 

 hydrogen sulphide, hydrogen, methane, oxygen, nitrogen, ammonia, 

 argon, and helium. 



The first attempt to produce power from natural steam was made 

 in 1897 by using it to heat water in a boiler and feeding a recipro- 

 cating engine with the pure steam. In 1905, Prince Conti fed steam 

 direct from a " soffione " into a piston engine, and the result was so 

 successful that in the following year a larger engine was used, and 

 the steam generated was made to drive a dynamo for lighting the 

 works. In 1912 it was decided to erect a 250-kilowatt turbo-generator 

 to be worked with natural steam, but owing to fear of corrosion of 

 the turbine blades, and the difficulty of obtaining a good vacuum in 

 the condensers, on account of the presence of the gases mentioned 

 above, this intention was abandoned. Intermediate boilers or 

 evaporators were therefore constructed and used. 



The present large power plant at Larderello was first operated in 

 1916, and comprises evaporators, turbo-generators, condensers, and 

 transformers. The evaporators employed, until recently, consisted of 

 vertical aluminum tubes inclosed in a shell of sheet iron; natural 

 steam circulated round them and the water to be evaporated through 

 them, this water being taken from the condensers or from that 

 formed by condensation of the natural steam. 



According to a paper which was read by Prince Conti at the 

 Catania meeting on April 5-11, 1923, of the Italian Association for 

 the Advancement of Science, this type of evaporator has been re- 



