144 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1940 



suddenly removed. Every electric light would go out. Every 

 electric motor would stop. Every automobile would become useless. 



Physical power is the basis of economic and national power. Pro- 

 fessor Leith, of the University of Wisconsin, has pointed out that it is 

 often said that the World War transferred world power from Great 

 Britain to America. But he believes that the World War onl}' made 

 evident what had already happened. In the nineteenth century, 

 Great Britain produced half of the world's physical power. Today, 

 the output of energy in the United States from coal, oil, natural gas, 

 and water power amounts to half of the world's total. It is this 

 fact, rather than the last war. Professor Leith believes, that explains 

 the dominant position of America in the world of today (5) . 



Any new source of energy, therefore, will be of supreme importance 

 to the future and a cheap and abundant source of energy will change 

 the shape of the future in ways which we can only attempt to guess. 

 As is well known to you, attempts are being made to find such sources 

 of power. 



It is being sought, first of all, in attempts to put the sun to work. 

 It would not be fair to say that the sun's energy goes to waste, since 

 its light and heat makes life upon this earth possible. But it is 

 perfectly true that we waste the greater part of the energy which the 

 sun sends us. It has been calculated that the amount of energy fall- 

 ing upon every square yard of earth's surface per second is the equiv- 

 alent of 11/^ horsepower. 



Physicists have long dreamed of putting this solar energy to 

 work. One of the first suggestions made was to concentrate the 

 sun's heat by means of mirrors upon a steam boiler. Dr. C. G. 

 Abbot, Secretary of the Smithsonian Institution, has been a pio- 

 neer in this field, and his solar engine (6), which has been ex- 

 hibited at meetings of the American Association for the Advance- 

 ment of Science, at the Great Lakes Exhibition in Cleveland, and 

 elsewhere, is well known to many of you. Dr. Abbot incorporated 

 many ingenious features in his device. A parabolic mirror con- 

 centrates sunlight upon the boiler which is actually two concentric 

 glass tubes with a vacumn between them. Thus while there is only 

 a slight barrier to the entrance of the sun's radiant energy, there 

 is a considerable barrier against the loss of heat by atmospheric 

 conduction. Steam is generated in the inner tube upon the flash- 

 boiler principle. 



Another method for the utilization of solar energy which seems 

 highly promising to many scientists is the conversion of sunlight 

 into electricity by photoelectric methods. 



About a year ago, on a visit to the research laboratories of the 

 Westinghouse Electric & Manufacturing Co. at East Pittsburgh, 

 I was shown four photoelectric cells like those used in light meters 



