between 12 and 30 per cent, of the total in periods ranging 

 between six months and one year. 



Results are also quoted which show that under certain con- 

 ditions and in the presence of an ample supply of organic 

 matter the nitrogen content of soils may show increases of 

 appreciable magnitude as tne result of the action of bacteria * 

 of the Azotobacter type, the existence of which has been 

 demonstrated in soils throughout the Colony. 



The importance of bacteria of the putrefactive type is 

 alluded to; these, by the continuous liberation of carbon 

 dioxide, assist in rendering available the mineral plant food of 

 the soil; energy for these and other bacterial processes is 

 supplied by organic matter. There is also the well-known 

 mechanical effect of organic matter on the character of soils. 



The results of a large number of manurial experiments on 

 various crops have conclusively demonstrated the necessity for 

 frequent applications of organic manures; these results have 

 been substantiated in other Colonies. 



The continued fertility of soils in the tropics seems very 

 largely bound up in the maintenance of the supply of organic 

 matter; more attention is necessary to this point in the tropics 

 than under temperate conditions, as owing to more favourable 

 circumstances it is used up much more rapidly by biological 

 processes. 



The question of the biological relationships of tropical soils 

 is of much interest and importance; the natural conditions are 

 particularly favourable to such development, and afford special 

 facilities for study; it is to be hoped that in the near future this 

 side of the problem will receive increased attention. 



FERTILITY SURVEY OF THE EGYPTIAN DELTA. 



By B. F. E. KEELING, M.A., 



Director of Physical Services, Survey Department, Ministry 

 of Finance , Egypt. 



[ABSTRACT.] 



Very extensive operations are now being carried out by the 

 Egyptian Government for the improvement of the drainage of 

 the low-lying parts of the Delta. At the suggestion of Lord 

 Kitchener it was decided to make a detailed survey of the 

 present condition of the land so that in years to come the 

 improvement effected by the works now in progress can be 

 assessed. 



The fertility map shown with the paper is that of the first 



