ASTRONOMY AND METEOROLOGY. 379 



while, the hot space in Africa, bounded by an isothermal of 86, has 

 extended and united itself with the hot space in Western India. In 

 June this line has reacted in Europe np to Christiania. In the south- 

 ern hemisphere the curves have become extremely flat. In July, the 

 extreme temperatures manifest themselves. Within an elongated 

 space, including Nubia and Southern Arabia, a line appears bearing a 

 temperature of 90s. But in Western India the temperature has also 

 become extraordinarily high since May. In Europe the isothermals 

 have overpassed the circular form, and begin to be convex in the in- 

 terior of the continent. In August, in the old continent, the east 

 side of Nova Zembla alone resists the still continuing tendency of the 

 curves to become more convex, and hence they assume two charac- 

 teristic convexities, one at Spitzbergen and the other at the mouth of 

 the Lena. But on the coast of Gicenland, as the drift ice decreases, 

 the isothermal curves become flatter. In September this is the case 

 in a still greater degree, and in Asia the convex summits are similarly 

 flattened. This is, consequently, the month when the distribution of 

 temperature over the globe is most regular. The isothermals of Oc- 

 tober show a decided invasion of cold from the north, and in November 

 and December they become, in both continents, concave. 



CLIMATE OF THE VALLEY OF THE NILE. 



AT the meeting of the British Association at Edinburgh, Mr. T. S. 

 Wells communicated a paper on " the climate of the valley of the 

 Nile," containing the results of observations made from December, 

 1849, to March, 1850. The mean temperature of the air for the 

 period of observations was, at Greenwich, 39 3', on the Nile, 61. 

 The mean temperature of evaporation at Greenwich was 37 4', in 

 Egypt 55. The mean temperature of the dew-point at Greenwich 

 was 34 1', in Egypt 50 8'. The mean elastic force of vapor in 

 Egypt was 0.384, at Greenwich 0.214. In other w : ords, the pres- 

 sure of the watery vapor mixed with the air was capable of support- 

 ing a column of mercury higher by .17 of an inch in Egypt than in 

 England. The mean weight of water in a cubic foot of air in Eng- 

 land was 3 grains, in Egypt 4.3 ; but still, owing to the higher tem- 

 perature, the air was much drier in Egypt. At Greenwich the mean 

 additional weight of water required to saturate a cubic foot of air was 

 only .4 of a grain, while on the Nile it was 1.3 grains. If we repre- 

 sent air completely deprived of moisture by zero, and air completely 

 saturated by unity, the mean degree of humidity on the Nile \vas 75 

 per cent., while at Greenwich it was 85 per cent. The mean readings 

 of the barometer in Egypt were 29.99, at Greenwich 29.87, but the 

 extreme range of the instrument was very small on the Nile. The 

 average weight of a cubic foot of air at Greenwich was 549 grains, in 

 Egypt 527. Rain fell in various districts of England on averages 

 from 31 to 61 days, in Egypt only 5 days, and on three of these a 

 shower lasted but few minutes. The mean daily range of the temper- 

 ature of the air at Greenwich was 11. 37, in Egypt 10. 31, but while 

 the mean extreme range in Egypt was 38, at Greenwich it was but 29. 

 Fog was very rarely observed . London Athenaum, Aug. 



