244 



NATURE 



[August 25, 1910 



dynasties, which throw some Hght on the early history 

 uf this region. 



• The author describes the ancient temple at Nha- 

 trang, stone built, with inscriptions in primitive Pali, 

 similar to those found in Nakhon Wat, and other 

 monuments scattered over a vast area. 



In conclusion, the book covers a wide field of in- 

 terest, and is a welcome addition to the literature 

 of further Asia. J- Thomson. 



LAKE CHAD.' 



THE first volume gives the geographical results of 

 the mission presided over by Captain Tilho (which 

 undertook, in connection with British delegates, a 

 delimitation of the Anglo-French frontier in the re- 

 gion of Lake Chad and northern Nigeria). The main 

 purport of this volume is the survey and delineation 

 of that extraordinarily puzzling feature in African 

 geographv, Lake Chad— a " lake " described by 

 Captain Tilho as being nothing but an immense marsh 

 with variable stretches of open water nowhere more 

 than 12 feet deep. 



Probably the first definite mention of Lake Chad 

 (under the name of Zad) occurs in the writings of 

 Frederick Hornemann, at the very close of the 

 eighteenth century. (Hornemann, who was taken 

 into the employ of the English African Association, 

 and sent by them to reveal this lake and also the 

 central course of the Niger, is believed to have 

 reached the Niger and to have died in the Nupe 

 country about 1800.) But rumours of a great sheet 

 of water in the heart of Africa, beyond the Sahara 

 Desert, had probably reached the Romans in the first 

 century of the the Christian era, through their con- 

 nection with Tunis, Tripoli, and Fezzan, and these 

 stories were reflected in the conjectured Libya Palus 

 of Claudius Ptolemeeus, who wrote in the middle of 

 the second century. When the Arabs and Moors had 

 become thoroughly acquainted with the geography of 

 the Sudan they revived these traditions, but mixed 

 them up with both the Niger and the Nile systems. 



As a matter of fact, the basin of Lake Chad is 

 curiously on the balance between the watersheds of 

 the Nile and of the Niger. The work of other and 

 earlier French expeditions (especially that of Dr. 

 Augusta Chevalier) which preceded that of Captain 

 Tilho has put before us evidence of a faunistic and 

 geological character which prompts the supposition 

 that Lake Chad is the very last vestige (shrinking 

 annually, one might say) of a vast, shalloit), inland 

 sea, which covered much of the region north, east, 

 and, above all, west of Lake Chad, of the basin of the 

 Niger north of the niountains, and probably 

 communicated with the sea along the basin of the 

 Senegal River. Whether there was any north-eastern 

 outlet towards the Nile basin is more doubtful. 

 Looking at the most recent map of Africa in relief, it 

 would seem more probable that there has been for 

 ages a bridge of high land through the Tibesti 

 country which has connected southern Tunis with 

 Central Africa, and separated the Niger-Chad basins 

 from that of the Nile ; but it is more likely that down 

 to the close of the Secondary epoch, or even at the 

 very beginning of the Tertiaries, there may have been 

 a connection between the Chad-Shari basin and that 

 of the Congo. Nearly the whole of the Congo basin 

 was, down to a relativelv recent period, a vast fresh- 

 water lake. A rise of ground so slight as scarcely to 

 be perceptible to the traveller separates at the present 

 day the basin of the Shari River from that of the 



1 RiSpublique Francaise. Ministere 

 fiquesde la Mission Tilho" (1906-9). 

 (Paris, Imprimdri 



Pp. Iv + 4' 



NO. 2130, VOL. 84] 



Mubangi-Wele, which, of course, marks the existing 

 limits to the north of the former Congo Sea, that 

 sea which in Tertiary times forced its present narrow 

 outlet through the Crystal Mountains into the southern 

 -Xtlantic. Many arguments for the justification of 

 these hypotheses (as also for arguing the relatively 

 early detachment of the Congo Sea from that of the 

 Sahara) may be found in the remarkable works of 

 Mr. G. A. Boulenger on the fresh-water fishes of 

 .\frica. From this same source, again, may be de- 

 rived further arguments for the relatively recent exist- 

 ence of the Chad-Niger Sea, and perhaps also for the 

 close geographical connection between that vast area 

 of fresh water and the great lake which formerly 

 filled up much of the Bahr-al-Ghazal-and-Upper-Nile 

 regions, a lake represented at the present day by the 

 Sudd region. 



Other French expeditions dealing with the country 

 between Lake Chad and the Mubangi-Congo have 

 established the existence (it is said) of the manati in 

 the Shari River, and, above all, in the isolated lakes 

 and pools to the north-east of that stream. The 

 manati is also stated to be found in the Niger River 

 between Sego in the west and Yauri in the east. If 

 this is really the case, it is further evidence for the 

 existence and the relatively recent drying-up of this 

 vast fresh-water Sahara Sea ; for the manati is a 

 Sirenian mammal the nearest relations of which are 

 found fossil in lower Egypt, in the West Indies, and 

 in Florida. The manati is still found as a living 

 animal in the estuaries and broader rivers of West 

 Africa, but it would be exceedingly difficult for it to 

 reach the L'pper Niger over the Busa Rapids, though 

 it might, and perhaps does, pass up the river Benue, 

 and thus reach the Shari by way of the Tuburi 

 marshes. (The manati is not found in the Upper 

 Congo.) With regard to these Tuburi marshes, we 

 have here a very interesting problem to discuss. 

 .Another French scientific expedition established not 

 long ago the feasibility of passing from , the Upper 

 Benue by canoe through the Tuburi marshes into the 

 Logun River, and thus into the Shari and Lake Chad. 

 Its leader (Lieut. Faure) has proved that at the 

 height of the rainy season of that particular year 

 there was continuous vi'ater communication between 

 the mouth of the Niger and Lake Chad, so that Lake 

 Chad was then nothing but a backwater of a river 

 system in Central Africa which sent a superfluity of 

 its waters to the Benue and the Niger. 



Captain Tilho's work, however, though it touches 

 on some of these hydrographical problems, deals 

 mainly with the configuration of Lake Chad, in 

 the volume under review. It shows that the average 

 depth of the lake is only i metre 50 cm. (say 4 feet 

 10 inches), and in the great stretches of open water 

 scarcely more than about 3 metres (say 10 feet). It 

 is simply a vast swamp joining the waters of the 

 Komadugu, which enters the Chad on the north-west, 

 with the floods of the Shari coming in on the south- 

 east. During the three years of study devoted by this 

 mission, the only area of open water remaining in the 

 Chad was quite outside British political limits, and 

 lay to the north and north-west of the Shari delta. 

 The rest of the lake surface was either completely dry 

 land (north of the Komadugu River) or it consisted 

 in the east of an archipelago of almost innumerable 

 islands interspersed with lagoons, pools, and navigable 

 creeks. Where Denham saw the waters of Lake 

 Chad at Ngigmi in 1S22 there may be a few tiny pools 

 or a small area of moist ground, but the rest of the 

 northern third of the lake has become absolutely dry 

 land. 



No doubt to the later expeditions of Earth and 

 Vogel the surface of open water in Lake Chad was 



