354 



Scientific Intelligence. [No. 8, new series. 



der falling on white paper was nevertheless well defined and red- 

 dish, showing that the illuminated paper had received rays of the 

 (complementary) bluish color. 



The blue color of the sun, though the light was gradually much 

 diminished, lasted until 5-10 p. m., when the sun had a height 

 only of about 15 degrees : then the disc soon disappeared entirely 

 behind the clouds of dust. 



The temperature of the air* was corrected for index errors on 

 the 3rd of April — 



Dry. Wet. 



At 12,, 

 1,. 

 2,. 

 3,, 

 4,. 

 5,. 

 6,. 



38 

 38 

 37 

 37 

 37 

 36 

 36 



19 

 19 

 19 

 19 

 19 

 19 

 18 



9 

 0 

 3 



3 } 



2 



1 



9J 



Direction of the 

 hot winds West, 

 very strong, from 

 12-45 to 6-10. 



The temperature of the air diminished, as occasionally noticed 

 in the observations above-mentioned, with the increase of the wind 

 and untransparency of the air. 



A coincidence worthy of notice is the sudden cessation of the 

 wind after sun-set, which took place at every one of my observa- 

 tions. Generally speaking, it is characteristic* of the hot winds ; 

 that in the beginning of the hot season the wind always ceases 

 very near sun-set, the night is very calm, and towards the morning 

 an Easterly breeze is not unfrequently felt. 



The cause of the hot winds ceasing with sun-set seems to be the 

 great depression of temperature during the night, coinciding with 

 the Westerly direction of the wind. In consequence the wind 

 meets, soon after sunset, with surfaces covered with a stratum of 

 air cooled by the vicinity of the radiating surface of the ground ; 

 the hot wind passes over it, and is therefore not felt near the sur- 

 face. 



* A room with tatties was easily kept at 25 Q to 27° C. in the centre of 

 the apartment, the wind being very strong. 



