( 503 ) 



tion from import-duties and placed some tents at our disposal ; and 

 lastly to the Compaiii'a del Norte who forwarded the luggage of the 

 eclipse party by express at reduced rates. 



The Secretary of the Committee 

 A. A. NIJLAND. 

 Utrecht, November 1905. 



Supplement I. Measii^rement of the heat produced hy the integral 

 radiation of the corona and of the solar dish, hy 

 Prof. W. H. Julius. 



The object of our heat observations was, as in 1901, 1^^ to settle 

 the question of 'the order of magnitude of the coronal radiation, and 

 2"<^, to determine the curve of the total radiation from the tirst until 

 the fourth contact, with the aim of deriving from it the distribution 

 of the radiative power over the solar disk. 



The investigation has been carried out with the same actinometer 

 that had been constructed for the Sumatra eclipse ^); in it the rays 

 are caught directly on a thermopile, without the intervention of lenses 

 or mirrors. As long as the radiation was sufficiently intense, absolute 

 determinations with Angstrom's pyrheliometer were also made at 

 intervals, in order to make sure whether the indications of our 

 sensitive actinometer might be considered proportional to the received 

 radiation. Such pi'oving to be the case even for intense radiations, 

 we were quite justified in assuming proportionality also to exist for 

 the feeble radiatioji falling beyond the range of the pyrheliometer. 



The astronomers of Madrid had a small house built in the obser- 

 vation camp ; thej^ kindly allowed us to dispose of one of the rooms 

 for setting up the galvanometer and performing the necessary 

 laboratory work. 



Four persons were required for manipulating the apparatus, two 

 inside and two outside the room. Mr. W. J. H. Moll, who has also 

 had a prominent share in the preparation of the observations and 

 the setting up of the instruments, was in charge of the absolute 

 measurements and of noting down all the readings together with the 

 corresponding times. The operations of directing and exposing the 

 actinometer and the pyrheliometer at signals, given by the observers 

 inside the room, were performed very punctuallj^ by P. Eleuterio 

 Martinez S. J., phys. prof, at Valladolid, and P. Antonio de 



1) Total Eclipse of the Sun. Reports on the Dutch Expedition to Karang Sago, 

 Sumatra, N". 4. Heat R.adiatiou of the Suu during the Eclipse, by W. H. Julius. 



