NO. 4 SITE FOR SOLAR-RADIATION STATION MOORE 5 



arrangement as shown in Figure 2 was employed, a was a circular 

 disk of slightly larger diameter than the opening in the hood, /;. The 

 latter was blackened within as was the under surface of disk, a. c rep- 

 resents the Angstrom pyrheliometer with the two blackened strips on 

 which the radiation fell. This arrangement gave a fairly accurate 

 measurement of the sky radiation adjacent to the sun, and while 

 water vapor also entered into the readings, it was possible to determine 

 in a general way whether the haze near the sun was due mostly to 

 water vapor or to scattering caused by dust and smoke particles. In 

 other words, on most days any deviation from the curve of uniform 

 pyrheliometry could be explained by nonuniformity in water vapor, 

 haze, dust, or smoke, or by combinations of these agencies. 



Fig. 2. 



In addition to these measurements, general meteorological records 

 were kept of the relative humidity, dry shade temperatures, wind direc- 

 tion and approximate intensity, and of cloudiness, fogginess, etc. 



It was planned that the expedition should leave the United States, 

 in January, 193 1. A few weeks before the time of departure, H. H. 

 Clayton of Canton, Mass., who has done much in correlating weather 

 changes with changes in solar radiation, suggested that the expedi- 

 tion should include in the itinerary a high peak on the island of Fogo 

 in the Cape Verde Islands, about 500 miles ofif the west coast of 

 Africa. About 25 years before, Mr. Clayton had been a member of a 

 French meteorological expedition that had visited Fogo, and he had 

 found such clear skies and other promising conditions on the island 

 that he thought it worth our investigation. 



A stop of a few days was made at Washington prior to sailing, in 

 order to acquaint ourselves with the apparatus and other details of 



