166 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1915. 



a solved problem where there is plenty of sunshine and coal costs 

 £3 10s. a ton. It is fortunate that where coal is dear sunshine is often 

 plentiful, and it is to be remembered that coal will gradually get 

 dearer while the cost of manufacture of sun-power plants should 

 decrease. Sun-powder plants are admirably suitable for pumping in 

 connection with irrigation, for where there is most sunshine there 

 is need for most irrigation, and the slight variation in the quantity 

 of water pumped throughout the day does not matter. Also, wdien 

 temporarily there is no sunshine (due to clouds), probably little or 

 no irrigation is required. 



In conclusion, the author would refer those who are interested in 

 the subject to his paper (8vo, 86 p., 22 illus.), bearing the same title 

 as this one, presented to the Society of Engineers on April 6, 1914. 

 Therein he dealt fully with the whole of Shuman's Work from 

 1910-1913, inclusive, and gave details of the results of the 62 trials 

 of the plant made by the author in England, the United States, 

 and Egypt. 



