MISCELLANEOUS SUBJECTS 467 



The heat absorbers are turned by the engine and their 

 speed of turning is regulated by an adaptation of the 

 thermostat which throws a friction clutch in and out. 

 The thermostat is located right under the boiler. As 

 long as the thermostat is in the shade this means that 

 the heater is pointing directly at the sun. When the sun 

 moves ahead a little then the edge of the sunlight strikes 

 the thermostat. It bends and immediately throws the 

 small friction clutch into place, and then all the heat 

 absorbers turn westerly a fraction of an inch or so. As 

 soon as the thermostat is again in the shade the clutch 

 is released and the sun heat absorbers stand still. 



In this way, by short intermittances, the heat absorbers 

 are always kept facing the sun throughout its course 

 during the entire day. 



The thermostat acts very satisfactorily indeed, and it 

 is interesting to see these large heat absorbers turning 

 apparently by their own volition steadily with the sun 

 as many plants and flowers do. 



The framework of the heat absorbers has been designed 

 in such a manner that by special machinery they can be 

 manufactured very cheaply. There are only eighteen 

 different kinds of pieces in the entire framework and each 

 piece is very simple. They can each be punched out at 

 one operation in a second. 



As the question of transportation to outlying tropical 

 districts is an important one, care has been taken that 

 all the pieces are light in weight; no piece weighs more 

 than 30 Ib. 



The heat absorbers at Cairo were erected entirely by 

 native labour under the supervision of one American 

 engineer in eleven days. 



Sun-power plants can be built of any size, from 5 h.p. 

 up to 10,000 h.p. if required. 



The heat absorbers at Cairo started to make steam in 

 midsummer about 7.30 o'clock in the morning, and kept 

 at work until 5.30 in the evening. 



Tests of the steam-producing capacity of these heaters, 

 made by Mr. A. S. E. Ackermann, of London, show that 

 the average production was 1,100 Ib. per hour of 15 Ib. 

 absolute steam for a ten-hour day, and this is equal to 



