The Abyssinian part of the catchment basin of the Blue Nile enjoys a good rainfall throughout nine months of the year from February to October, with generally heavy rain between May and September, and very occasionally in October. The rainfall here may be taken as 1.25 metres per annum. In the plains of the eastern Sudan traversed by the lower reaches of the Blue Nile and the Atbara the rainfall is very much lighter and may be considered as 30 centimetres between July and September; fairly constant and heavier in the south, and very inconstant and lighter in the north. The Atbara and its tributaries in their upper reaches on the northern slopes of Abyssinia, have rain from May to the end of August and occasionally into September. There are great fluctuations in the rainfall. The mean annual rainfall may be taken as 75 centimetres. The desert area between Khartoum and Cairo has occasional winter rains especially in the parts near the Red sea, but as these rains are nearly all soaked up by the desert, and very little, here and there, reaches the Nile, we may neglect them altogether. Railways have to be provided with culverts and bridges where they cross the terminal reaches of the khors and wadis which run considerable bodies of water for a few hours after rain; but the effect on the Nile is practically nothing. Along the sea-board of the Mediterranean there are a few inches of rain every winter, sufficient as a rule to raise poor crops of barley. In the catchment basins of Lakes Victoria and Albert the direction of the winds may be taken as north-east in winter and south-east in summer. The maximum monthly temperature may be taken as 35° and the minimum as 12°, with a mean for the year of 21°. Along the Albert Nile the north wind blows through the winter, and southerly winds prevail from about the 15th of April to October. The temperature may be taken as ranging from a monthly maximum of 38° to a monthly minimum of 16°, with a mean of 27°. Tables 75 to 81 give the principal meteorological data for many places in the Nile valley and compare the Bombay rainfall with the Assuân gauges. The latter show how closely the Assuân gauge in flood follows the rainfall at Bombay. At Addis Ababa in the highlands of Abyssinia, the mean monthly temperature ranges between 19° and 15°, with a mean of 17°. The winds are south-east and east through the year. In 1902 the rainfall was 980 millimetres, and in 1903 it was 1340 millimetres. (Table 75). At Wad Medani in the Grezireh south of Khartoum, the mean monthly temperature ranges between 35° and 24°, with a mean of 30°. The winds from October to April are from the north and from May to September from the south. In 1902 there were 350 millimetres of rain and in 1903 there were 310. (Table 76).