GEOLOGY 79 



undergi'ound supplies near the centres of civil and military adminis- 

 tration. The work closed down in 1931, after a certain measure of 

 success, but was started again in 1935, with a new scheme, under 

 which several centres of population and grazing areas have been 

 supplied satisfactorily. 



Turning to West Africa, the greater part of geological activity 

 in Nigeria is devoted to water-supply, especially in the Northern 

 Provinces. Surveys of underground water have been carried out 

 along the northern frontier in the region where it is alleged that 

 the Sahara Desert is advancing. Since 1927, when, after a period 

 of dry years, attention was focused on the water problem in 

 Sokoto, geological investigations have been carried out in that 

 province, and also in Bornu and Hadejira Emirates. It is con- 

 cluded provisionally that right along the northern frontier of 

 Nigeria water can always be tapped at depths from one hundred to 

 one hundred and fifty feet. Since it occurs in sub-artesian basins, 

 the water is generally under pressure and usually rises to the level 

 of ground water. The deepest shaft constructed measures three 

 hundred and seventy feet, while the highest pressure rise recorded 

 is one hundred and nineteen feet, although there are several of 

 over one hundred feet. By the end of 1935, seven hundred and 

 ninety-three wells had been completed. The work of sinking is 

 financed almost entirely by the various native administrations to 

 the extent of about ^^ 18,000 per year, but the cost of all geological 

 investigations and of the administration of the work is borne 

 by the government. The department now advises on all water- 

 supply projects, whatever their nature and scope, and controls 

 and carries out all work connected with sub-surface supplies. In 

 the Southern Provinces a power-driven drill is now at work at 

 Otta, twenty-three miles from Lagos. A scheme for open wells 

 has been approved also for Owerri Province, where permanent 

 running streams are so widely spaced and the population pressure 

 is so great that serious water shortage occurs during the dry season 

 in spite of an annual rainfall of one hundred inches. Full details 

 of investigations on Nigeria's water-supply are given in recent 

 annual reports of the geological department, and in addition 

 Beeby Thompson (1933) has discussed the water problems as a 

 whole, while the geology and water-supply of parts of the Northern 



