292 § ANNUAL REPORT SMITHSONIAN INSTITUTION, 1958 
equipment costs. Research on solar stills having that and increasing 
efficiencies as objectives has been carried out by the Office of Saline 
Water [22, 23]. Both glass and plastic membranes have found ap- 
plication as transparent covers for solar stills, and equipment costs 
are being reduced. 
A number of typical American still designs, some intended for re- 
search use only, are shown in plate 2 and plate 3, figure 1. They 
include stills of suspended-envelope type, canopy type, and flat tilted 
type. Their output was found to be, rather uniformly, about 1 pound 
of fresh water per square foot per average day of sunshine in a mod- 
erately warm climate. 
Small solar stills have had extensive practical development in 
Algeria and Morocco [24] and Australia [25]. Manufacture of stills 
with effective surface of 10 to 12 square feet is reported for one 
maker in Algeria, while another has developed a much larger still, 
to be made up of jointed units 10 by 40 feet each. 
A design for a deep-basin still with an area of 5,000 square feet, 
to be built directly on the ground, was prepared in 1957 by George 
O. G. Lof of Denver, Colo. (pl. 3, fig. 2). 
The Office of Saline Water has initiated a comprehensive develop- 
ment program on solar stills through contract with Battelle Memorial 
Institute of Columbus, Ohio. Prototypes of various existing and im- 
proved designs are being installed for further development at a cen- 
tral seashore test station near Port Orange, Fla. The first small pilot 
plant of the L6f deep-basin still is now being constructed there. The 
next two prototypes to be built will be of plastic films in place of the 
glass. The new plastic has been developed by the Du Pont Co. of 
Wilmington, Del. One will be based on the design shown in plate 2, 
figure 2, using an air-supported transparent cover, and will also have 
an area of about 2,500 square feet. Low-cost preformed concrete 
bases under development are expected to reduce costs further and 
greatly simplify field construction. The second Du Pont type of 
about 500 square feet was originally designed to utilize a wire sup- 
port for the plastics cover (pl. 4, fig. 1). However, within the last 
few weeks Du Pont has prepared a folded or pleated film which 
promises to remove the need for the wire support and further reduce 
costs. Others to be installed and tested at the Port Orange research 
center are the suspended envelope developed by Bjorksten Labora- 
tories of Madison, Wis., and the tilted stills developed by Maria 
Telkes of New York University, both under the direction of the Office 
of Saline Water. 
A need exists for two major types of solar-distillation equipment: 
small stills, some of which may be portable; and large-capacity stills. 
The small stills should have production capacities that range from 
