56 Mr Buchanan, On a solar Calorimeter used in Egypt 



Meteorological Observations and Notes. The climate at Sohag 

 is a desert climate tempered by the influence of the Nile. This 

 influence extends only a very short distance from the banks of the 

 As the population is confined to the banks of the river its 



river. 



benefits are enjoyed by the whole population. During the few 

 days in May that the expedition sojourned at Sohag the sun 

 attained a meridian altitude of roughly 83°, so that its power 

 differed very little from that of a vertical sun. The prevailing 

 wind is from the North which gives a freshness to the atmosphere 

 while it also enables the countless sailing craft on the Nile to 

 navigate its waters against its not insignificant current. 



While occupied with the calorimeter I made observations on 

 the temperature of the air using both the wet and dry bulb 

 thermometers, and I also measured the evaporation by night and 

 by day of water exposed freely in a plate raised about 6 inches 

 above the ground. A glance at Table II. or Fig. 7 which contain 

 these results will indicate better than any description the nature 

 of the climate in that part of Egypt in May. 



Fig. 7. Meteorological Observations on the 16th, 17th, and 18th Mat, 1882. 



The latitude of the station was 26° 37' N. so that, on the 

 ocean, it would be in the heart of the Trade Wind. In fact 

 the Trade Wind regions of the ocean are the desert regions of the 

 sea. The water at the surface is there drier than anywhere else, 

 that is, a given volume of it contains more salt and less water 

 than is to be found either on the equatorial or on the polar side 

 of the region. The northerly wind on the Nile is the Trade Wind 

 blowing from colder to hotter latitudes and always increasing its 

 evaporative power. Thanks to this power the temperature of 

 the Nile is lower than it would otherwise be. I took its 

 temperature frequently at all hours of the daj^, it varied only 

 between 74*5° and 76° Fahr., while the temperature of the air 

 above it varied from 50° to 105° Fahr.; the variations of the wet 



