270 Dr. G. B. Longstaff on sible. However, Mr. Willis has been most kind in giving me all the information at his disposal, and I have pleasure in quoting at some length from his quite admirable letters in reply to my numerous queries.

" The season would be after the rains, when the country is still green and water lying out in places." Among Mr. Willis's kind acts was putting me in possession of the official guide-book, entitled " Kordofan and the Region to the West of the White Nile ; Compiled in the Intelligence Department, Sudan Government, Khartum," Dec.

1912. From this book, which is not to be obtained through the usual channels, I learned that : The end of the rainy season, when the crops are ripened but still uncut, is in October or November; in the south the first rain-storms may be expected as early as the beginning of March (p. 14). This confirms Mr. Willis' statement, but seasons, even in the tropics, vary, and in considering statements as to " dryseason " or " wet-season forms," it must not be forgotten that "wet" individuals may, and often do, survive some way into the dry season.

Again, we have this statement : " The places mentioned are probably about 400 ft. higher than the White Nile, but there is very little to go on." Khartum is said to be 1200 ft. above the sea; Kaka is 404 miles higher up the river than Khartum, and is in about the same latitude as Talodi, the headquarters of the Nuba Mountains Province. Now the guide-book (p. 69) states that Talodi is 2000 ft. above sea-level ; from this we may deduce that the White Nile falls 400 ft. between Kaka and Khartum. That is all that I have been able to find out ; the two statements seem fairly concordant.

" Kadugli and Dilling are villages situated in the plain in the vicinity of hills, with a ' khor ' or rain-fed stream, only running as a rule for a few hours at a time, close by.

" Sungikai is on a biggish khor, lying somewhat north of the hills, running through what we call ' forest ' here, which means a rolling country covered with trees about the size of an apple-tree, grass, etc., which dries up in winter, and turns green again as soon as the rainfall about the end of May.

" Tira Mandi and Tatcho are both hills—rough granite blocks with practically no vegetation on them except where the black Nubawi terraces the land, which he does