34 o On a solar Calorimeter ^lsed in Egypt 



During the three days, the i6th, I7th and i8th May, the 

 conditions were very favourable, and particularly so on the 

 forenoon of the i8th when the sun was intensely hot and 

 the atmosphere motionless. On none of these three days 

 was the sun at any time obscured by cloud. The only inter- 

 ference with the sun's rays was by dust, with which the desert 

 air is always charged. It made itself evident by settling upon 

 the mirror surfaces of the reflectors, where it formed a dust of 



Fig. i. Fig. 2. 



infinite fineness which could only be seen when regarded 

 edgewise. The results obtained on the forenoon of the i8th 

 are to be taken as the best. 



Figs. I and 2 are photographic representations of the 

 instrument showing its general appearance and arrangement. 

 Fig. 3 gives a section of the calorimeter, and Fig. 4 a per- 

 spective view. 



