96 FROM THE NIGER TO THE NILE 



were very friendly, and brought us plenty of food, and on 

 July 5 we marched on to Dugurh. All through the Angoss 

 country the route was hilly and rocky. So hard indeed 

 was the ground that one of my horses could not be ridden 

 again for two months, as its hoofs were worn down almost 

 to the quick. About here too, we came across an extra- 

 ordinary amount of mica — the path we followed shone with 

 it like silver, and on either hand we could see great sheets 

 of it. There is very little grass, and few bushes, and it must 

 have been very difficult to grow crops in such a stony soil. 

 The whole land was mapped out into little terraces, sometimes 

 only a foot or two broad, built to hold up the rain as it ran 

 down the hill, and prevent the soil from being washed away. 

 In places no longer cultivated, only the dilapidated terrace 

 walls remained, through the rents of which in course of time 

 the soil had been blown or washed down. In this case one 

 saw only low walls encircling a hill, and I cannot but think, 

 though with deference to the views of Dr. Randall Maclver, 

 that a similar cause may have led to the erection of the 

 extraordinary systems of concentric walls, which exist in 

 Rhodesia. It seems to me hardly probable that any nation 

 should have constructed rows of even twenty parallel walls, 

 so near to one another up the sides of a mountain, for the 

 purpose of fortification. As a matter of fact, I believe that 

 the number of concentric walls which have been found 

 girdhng a Rhodesian Hill sometimes reaches a hundred or 

 more. The obvious objection to the irrigation theory is 

 that the walls in Rhodesia are, I believe, several feet deep 

 on the inside, while in Northern Nigeria they are seldom 

 more than a foot. This might be explained, however, by 



