rRESIDKXTJAL ADDRKSS SECTION A. 



25 



cuncciurating' apparatus, that solar slcani is many times more 

 costly than steam pruchicod by burning fuel."' 



Owing to the diffuse nature of the sun's rays, there is great 

 difhculty in trapping them etiiciently for practical purposes. 

 Some of the methods, such as the one of Shuman's shown by 

 V'xg. 2, make no effort to concentrate the heat rays, flere the 

 principle employed is that of the garden forcing- frame, in which 

 the rays are absorbed directly, the apparatus consisting of a 

 shallow Hat box covered with two layers of window glass, to 

 minimise loss from radiation. Coils of piping, painted black, 

 were placed in the box, these containing the water which was 

 converted into low-pressure steam. This ex])erimental plant, 

 erected at Penns3lvania in .1907, had a glass area of 1,080 sq. 

 feet, gave a steam pressure of 15 lb., and developed 33/2 h.p. 

 Naturally a company was formed to exploit the invention, and it 

 was stated that " if the results which are foreshadowed by the 

 experimental plant are confirmed by more extended trials, one of 

 the most perplexing problems will have been solved.*' 



Efforts were afterwards directed to the system of concentrating 

 the sun's rays on a boiler, by means of parabolic reflectors, and 

 the first plant on a commercial scale was built by Shuman, at 

 Philadelphia, where 32 h.p. was obtained at mid-day with an 

 average of 14 h.p. during eight hours of the day. The experience 

 gained from this plant was utilised in the plant erected at Meadi, 

 near Cairo, in Jtine, 1913. This solar engine, one of the parabolic 

 reflectors of which is shown in Fig. 3, is used for jiumping water 



Fig. 3. — Solar Plant at ^Meadi, near Cairo. Egypt. One of the focussing 

 mirrors which concentrate the sun's rays on the boilers. 



for irrigation. It was visited in 1914 by Air. Ingham, one of the 

 Members of our Council, and a description was given by him in his 

 presidential address to the S.A. Institution of Engineers in 191 5. 

 Parabolic reflectors are used, constructed out of ordinary window 

 glass, silvered on the back. There are Ihxe such absorbers, each 

 200 feet long and 13 feet wide at the top, constructed of light 

 structural steel, the light reflected from the mirrors being caught 

 on the two sides of the long boilers made of thin ca^t-iron. which 



