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 
river. As the population is confined to the banks of the river its 
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 May, 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 day, 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 
