26 presidi:ntial aodrkss — section a. 



arc suspended at the focus, so that every 5 sq. feet of sunHght 

 received by the mirror is concentrated on i sq. foot of the boiler. 

 Steam is generated at atmospheric pressure and utihsed in a 

 specially-designed low-pressiu-e condensing engine. It is claimed 

 by the inventor that high-pressure steam could be generated, but 

 that radiation losses would be excessive. The heat absorbers, 

 carrying the boilers, are attached to rollers and gears carried on 

 concrete foundation-posts, and are turned slowly so as to face 

 the sun at all times of the day, this being done automatically by 

 means of a thermostat, which starts and stops the driving gear 

 from the engine. Special provision is made for expansion and 

 contraction, and the boilers are covered by a thin sheet of window 

 glass. A wind pressure of 30 lb. per sq. foot has been allowed 

 for. 



Fig. 4. — Outline Map of Africa, showing the portion of the Sahara Desert 

 which, according to Shuman, would have to be covered with sun heat 

 absorbers to obtain every year a heat value equivalent to that of all 

 the coal mined in the world in the year jqoq. 



Tiie engine is capable of dcvelo])ing 30 h.p. and constinies 

 22 lbs. of steam per i h.p. hour. The maximum power ol^tained. 

 however, has been ig.i h.j).. and in view of the fact that the i)lant 

 occupies % acre this has to be compared with the 7,000 h.p., 

 which is the power equivalent of the radiant heat received. 



Mr. Ingham considers that this plant has not proved a com- 

 mercial success. The essentials for stich would be a reasonable 

 first cost, and the estimated cost of the Cairo plant was £1.560, 

 or £31 per h.p. even if 50 h.p. were obtained, or over £80 |)er h.p. 

 based on the maximum power developed. There must also be 

 an absence of high maintenance charges, and the plant must be 

 simple in operation ; these conditions it is claimed are fulfilled. 

 The mechanical constrtiction must also be stich that the strongest 

 winds may be resisted. Assuming that 50 h.]). could be obtained 

 per acre, a t, 000k. w. plant wotild occu])y about 27 acres. Btit prob- 

 ably, apart from the high initial cost and the tinweildly nature 

 of the i)lant, the principal drawback is the intermittent nature of 



