52 THE TANGANYIKA PROBLEM. 



throughout a great part of equatorial Africa, and the extra- 

 ordinary complexity of which we are only just beginning to 

 understand. The two greater longitudinal series, which 

 were first known, have been likened by Suess to the crack- 

 like " rills " that traverse the surface of the moon ; but in 

 their present complex aspect they appear to me to be far 

 more closely comparable to the so-called canal systems 

 which can be seen to form a dark lacework over the 

 equatorial portion of the planet Mars. I do not intend 

 to push this comparison any further, but it might be 

 fruitful to bear in mind that these equatorial, terres- 

 trial, and martian networks, are certainly in some respects 

 analogous. 



In considering these remarkable folds still further, 

 we find, as one of their most striking features, that 

 their floors are more or less invariably strewn with 

 active and extinct volcanic cones. We may say, in fact, 

 that along any of these great valleys we have only 

 to go far enough in order to encounter past or present 

 evidence of intense volcanic activity and terrestrial imper- 

 manence. Thus the short series to the east opposite 

 Mombassa contains Kilima Njaro and its associated cones. 

 The Beringo series contains many extinct volcanoes, such 

 as Longonot, and further to the north the active cones 

 which have been found in the neighbourhood of Lake 

 Rudolf, while finally, all along the floor of the vast 

 western series of valleys in relation to Tanganyika, we 

 have equal evidence of past and present volcanic activities. 

 Often as in the case of the Mfumbiro chain on a gigantic 

 scale. 



This relation in Africa of the volcanoes of the continent 

 to the floors of the eurycolpic folds is not, however, diffi- 

 cult to understand ; we have seen that these valleys have 



