( 504 ) 



Madariaga, S. J., tbeol. prof. at Burgos, to whom we express once 

 more our sincere thanks for tlieir very vahiable assistance. I myself 

 regulated the resistance in the circuit of the thermopile, and read the 

 o-alvanometer deflections. 



o 



The conditions for measuring radiation were much more favourable 

 now at Burgos than during the J 901 eclipse at Karang Sago; for 

 then the phenomenon was permanently veiled by rather thin clouds 

 of very variable transparency, co\'ering the whole sky; this time 

 heavy clouds caused the Sun to be indeed absolutely invisible now 

 and then, but between the epochs of the first and the fourth contact 

 there were intervals i]i which the plienomenon showed itself in per- 

 fectl}" clear patches of the tirmament. The favourable periods have 

 all been utilized; thus we were able to determine some parts of the 

 radiation curve very sharply. After (he results of the 81 observations 

 had been plotted down on millimeter paper, we saw that the missing 

 parts of the curve could be inserted with a fair chance of exactness. 



Fortunately the time between second contact and 11 minutes after 

 third contact was among the favourable periods. This period, however, 

 had been preceded by full half an hour during which no obser- 

 vations could be made ; and as the rift in the clouds, through which 

 totality just became A'isible in our camp, came quite suddenly, we 

 were not prepared and lost at least a minute after second contact 

 in arranging oiu' apparatus for highest sensitivity. Nevertheless we 

 compared three times the radiation of the corona with that of a 

 portion of the sky at a distance of about four degrees from the Sun. 

 The observed deflections were 9, 13 and 33 scale divisions; then a 

 sudden increase showed that totality was over. The effect produced 

 by full sunshine corresponded to 1800000 divisions, when reduced 

 to the same resistance of the circuit. So the smallest effect observed 



during the total eclipse was ^ — of the radiation of the uneclipsed 



Sun, or about -,'5 of the radiation of the full Moon. This value 

 must be considered as an upper limit to the radiation 

 emitted by those parts of the corona, which were not 

 screened by the Moon at the epoch of central eclipse. 

 Indeed, the radiation must pass through a minimum about the middle 

 of totality, and we are not sure that the first of tlie three obser- 

 vations above mentioned corresponded exactly to the central position. 

 Moreover, since a few thin clouds may have traversed the compared 

 fields, there is some uncertainty left. 



An account of the observations made before and after totality and 

 a copy of the resulting radiation curve will be found in the com- 



