464 MISCELLANEOUS SUBJECTS 



explains what is meant by " concentrating sunlight." If 

 we keep on throwing in light rays in this way we would 

 finally reach temperatures which would melt steel and 

 even the hardest metals. This is not merely a theory; 

 steel has been melted with concentrated sun rays, and a 

 sixpence has been melted in 7! seconds. Sunlight can 

 be concentrated by lenses, but this would cost too much 

 for power purposes. The concentration of sunlight by 

 means of funnel-shaped reflectors also presents practical 

 difficulties which make this method too costly. 



In order to generate steam very high concentrations 

 are unnecessary, and therefore we use in our Egyptian 

 sun-power plant only five concentrations by means of 

 mirrors. 



After seven years of patient experimental work and 

 the expenditure of very large sums of money we have 

 finally solved the problem of producing mechanical power 

 from the sun's rays, and have erected a 5O-h.p. sun-power 

 plant at Maadi, a suburb of Cairo, in Egypt. Cairo is 

 30 North, and is by no means the best place to put up 

 a sun-power plant; but it is easily accessible, and as we 

 wanted to exhibit our sun-power plant to the world we 

 erected it there rather than in (we will say) the Sudan, 

 where few people would go to see it. 



All our figures and remarks are based on the actual 

 performance of this plant, and as we know it would do 

 even better work further south, we can consider our 

 figures very conservative. 



Unless sun-power can be utilized profitably there is, of 

 course, no incentive to spend money and work upon it. 

 Therefore the question of pounds, shillings and pence is 

 an all-important one. As our fuel costs absolutely noth- 

 ing, the question of mechanical efficiency does not enter 

 into the matter. It is a question altogether of the cost 

 of the construction, upkeep, and labour. If the cost of 

 construction of the sun-power plant is so high that the 

 interest on the extra investment (above the cost of a 

 steam plant of equal capacity) will be so great that it 

 cannot compete with coal even at a point where coal is 

 very costly, then there will be no incentive to go further. 

 If the sun-power plant cannot be so constructed that an 



