( 505 ) 



plete report shortlv to be published. The shape of the unscreened 

 part of the solar disk being known for every monient, and the 

 corresponding radiation being given by the ordinates of the curve, 

 we have the data for calculating how the apparent emissive power 

 increases from the limb unto the centre of the disk. This method 

 avoids certain sources of error by which the results must be disturbed 

 when the distribution of the energy is measured in an image of the 

 Sun, viz. : the dilfusion of rays by the Earth's atmosphere and by 

 the optical train, as well as the consequences of variable radiation 

 emitted by the apparatus. We find a greater difference between the 

 heat from the limb and that from the central parts, than has been 

 obtained by the other method. According to our measurements the 

 decrease of the integral radiation from the centre to the limb follows 

 iiearly the same law that was found by H. C. Vogel, with the 

 spectrophotometer, to hold for rays of wave-lengths between 500 

 and 600 ftfi. 



Supplement II. The prismatic camera. By Prof. A. A. Nijland. 



The prismatic camera was mounted above the northern polar 

 mirror in such a manner that the dispersion direction is almost 

 perpendicular to the expected crescents of the first and the second 

 flash. 



The programme was as follows : 



1^' flash : 5 exposures, each of ^j^ second on one plate at intervals 



of 3 seconds ; 

 totality : 2 corona exposures, each of one minute and a half, at two 



different positions of the instrument so that the plate in the 



second position might show a part of the spectrum which 



did not occur on the first corona plate. 

 2"^^ flash: 5 exposures in the same manner as those of the I^t flash. 

 Cadett's spectrum plates were used. 



As soon as we found that we could not count upon assistance 

 of volunteers I had after some training acquired the necessary 

 skill to carry out this programme, yet I disliked the prospect of 

 having to do everything entirely by myself. Therefore I gladly 

 accepted the help of Dr. J. Kaplan (from St. Petersburg) who, having 

 arrived at Burgos on August 29, immediately offered his assistance. 

 I wish to express here my cordial thanks to him for his skillful aid. 



