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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65 



of the degree marks is naturally less wide than it would have been if 

 time had been allowed for full photographic effect at the extremes 

 of the swing. 



SUMMARY OF READINGS AND REDUCTIONS 



The solar radiation indicated by the mean value of the first three 

 records, which are by far the best, is 1.761 calories per sq. cm. per 

 minute. Reduced to mean solar distance and adding 1 per cent for 

 clock rate, it becomes 



1.84 calories per sq. cm. per minute. 



As will be shown, the mean altitude at this time was about 22,000 

 meters, and the corresponding pressure about 3 centimeters. In our 

 opinion an increase of about 2 per cent would be a proper allowance 

 for the extinction in the atmosphere above this altitude, considering 

 atmospheric scattering as 1 per cent, and atmospheric absorption 

 1 per cent. 



BAROMETRY AND ALTITUDE 



The following results are given by the observations of the U. S. 

 Weather Bureau, as indicated in communications quoted : 



