i6 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. J'J 



retically and by the expedient of drawing several hundred numbers 

 from a bag containing positive and negative numbers equally, and. 

 arranged in magnitudes in accord with the probability curve. 



So the average deviation of either station from the angel's curve 

 is 0.0078 calorie. The probable error, therefore, of the daily measure- 

 ment of either station alone is 0.845x0.0078 or 0.0065 calorie. 

 But there are many cases available where both stations observed 

 on the same day. In these cases the probable error of the general 



. 0.0065 . 



mean is — ^j=^ or 0.0046 calorie. 



I wish it to be realized fully that we do not have to guess at the 

 probable error of our determination of the solar constant. Our 327 

 observations at two stations give abundant material to determine 

 it accurately. As remarked above, we do not pretend to claim that 

 constant errors of scale are included in these small probable errors, 

 which are respectively 0.0046 calorie for general mean results of 

 both stations, and 0.0065 calorie for mean results of a single station. 

 But the possibility of systematic errors of scale has nothing to do 

 with the question of short-period variability. 



Having thus obtained the probable error values, we next inquire 

 whether the results, when the long swings of the solar constant which 

 critics have sometimes admitted may be probably real are shut out, 

 still exhibit solar fluctuations. To eliminate the long swings, I make 

 use of the monthly mean values, and take daily departures therefrom. 

 I separate these daily departures from the monthly means into two 

 series, the first containing days observed at both stations, the second 

 containing days observed at one station only. The numbers of 

 observations are 398 and 744, respectively, in the two series. 



Taking the first series of 398 days observed at both stations, the 

 numbers of departures from the monthly means, grou]>ed in magni- 

 tudes, are as follows : 



