( 67J ) 



Oh p. 670 the equations ave written out. We have confined our- 

 selves to 13 equations ; increasing this number would not have led 

 to greater accuracy, as tlie values of n, />,(■... had to be found from 

 the radiation curve, that is bv graphical interpolation, in which pro- 

 cess it is understood that all of the observations have already been 

 taken into consideration. 



Determination of the constant terms of the equations. 



Table I contains the results of the observations made at Burgos 

 with our actinometer. The second column gives the galvanometer 

 deflections, from which the numbers of the third column, representing 

 the intensity of the radiation, are calculated '). 



Owing to the clouds there are large gaps in the series of obser- 

 vations ; but nevertheless, after the results had been plotted down, 

 we saw that there was only little room left for fancy when drawing 

 the radiation curve in such a way, that closest agreement with the 

 observational data was obtained. As a matter of course the curve 

 has not been drawn between the se7nes of points, but so as to join 

 the highest points, for the observed values could only be too small. 

 Only one exception is made to this rule, the value found at 0'' 17™ 3' 

 being very probably too high by some error or instrumental dis- 

 turbance. 



The middle part of the radiation curve has been reproduced on 

 the annexed plate. For determining a, b, c, . . . we have used the 

 part included between 0'' 55™ and I'' 37™ , which was very carefully 

 constructed on a lai-ger scale. It deserves notice that the relative 

 accuracy of the small ordinates (corresponding to few minutes after 

 totality) is nearly as great as that of the larger ones, because 

 the galvanometer deflections from which they were calculated are 

 all lying between 118 and 347 scale divisions. Table II refers to 

 this part of the radiation curve. In the second column are given 

 the ordinates of the curve at the epochs 0'- 55"' 40^ and every 

 two minutes later ; the unit corresponds to 'an intensity = 1000. 



1) Particulars concerning the connection between the numbers of these two 

 columns will be found in the forthcoming report on the Dutch expedition. The 

 method and the instruments used al Burgos were the same that are described in : 

 'Total Eclipse of the Sun, May 18, 1901. Reports on the Dutch Expedition to 

 Karang Sago, Sumatra, N'. 4: Heat Radiation of the Sun during the Eclipse", by 

 W. H. Julius. The numbers of the third column are proportional to the total 

 radiation coming from a circular patch of the sky, 3° in diameter, with the Sun 

 in its center. 



