28 



PKESIDKNTIAL ADORICSS— SECTION A. 



Hence its overwhelming value to posterity and its capacity for 

 practically infinite expansion." 



" One thing I feel sure of," he adds, " and that is that the 

 human race must finally utilise direct sun-power, or revert to 

 barbarism, and I would recommend all far-sighted engineers and 

 inventors to work in this direction to their own profit and the 

 eternal welfare of the human race." 



A coalless world will not be so bad after all if onlx' Mr. 

 Shuman's advice is taken. 



Other devices are shown in Figs. 5 and 6. 



I am informed that the system is in use in California and 

 other parts of America for heating ])urposes. There seems no 

 reason why it should not l)e developecl in this direction. cs]uxMally 

 in South Africa. 



Fig. 6. — Suggestion to combine solar energy and a fuel-heated boiler 

 for an ammonia engine. 



JVind Poivcr. — Currents of air have been em])loyed from the 

 earliest times as a moti\^e })ower for marine ]jro])ulsion ; and 

 sailing ships, at the present day, ])lay a by no means negligil)le 

 part in the carrying power of the world. Ihil the variation of the 

 wind in intensity and direction has militated against the general 

 adoption of wind prime-movers. The earliest authenticated record 

 of the erection of a windmill bears the date tiqi. but there is 

 reason to believe that it is of earlier origin. The crude con- 

 struction of the earlier types have given way. under scientific 

 engineering treatment, to the modern forms, but used as t hex- 

 mainly have been for corn-grinding, they could not ho])e to com- 

 pete with modern prime-movers or electric supply giving a reli- 

 able and continuous source of ]K)wer. and have consequently only 

 siuwived in isolated parts, and mainly for small pumping ])lants. 

 driving light farming machinery, and to a \erv limited extent for 

 the generation of electricitw l-^or such ])uriioses. a considerable 

 industry has been (levelojied. It was recently stated that tlic 

 production of windmills in the L^nitcd .States had increased four- 

 fold during the ])r(.'\-ious ten years, and the making of windmills 

 now constitutes, I believe, one of om" few .'^outh African indus- 

 tries. 



While the drawbacks are to a great extent similar to those 

 for sun-])ower. there can be no denying the fact that a windmill 

 is an exceedingly convenient motor. The motive fluid costs 



