June 12, 1896.] 



SCIENCE. 



859 



courses of the narrow }'oung Pleistocene 

 valleys are inherited from similarly curved 

 courses on, the flat floors of the old Tertiary 

 valley-troughs in which the young valleys 

 are incised ; while the relative straight- 

 ness of the Missouri is ingeniously explained 

 as a consequence of its comparatively re- 

 cent entrance into this region, after uplift 

 in the region of the great plains. 



COASTAL DESERT OF PERU. 



Major A. F. Sears describes the coastal 

 desert of Peru in a recent Bulletin of the 

 American Geographical Societj^ (xxvii., 

 1895, 256-271). The desert belt has its 

 greatest width near latitude 5° S., where 

 it measures about 120 miles to its inner 

 margin, 1,000 feet high along the base of the 

 western Cordillera; thence narrowing south- 

 ward but extending about 2,000 miles along 

 the oblique part of the South American 

 coast. The surface is barren, except along 

 the few river courses ; crescentic dunes, or 

 medanos, frequently occur; the drifting sand 

 produces a sighing sound, like that from a 

 forest under the wind. From December to 

 March winds set on shore and give some 

 rain to the Cordillera (apparently ' subequa- 

 torial rains'); then the rivers flow again, 

 after having withered in tlie dry season. A 

 graphic description is given of the ' coming 

 of the river ' in the case of the Piura. In 

 February or March, when it is expected, 

 travelers from up the valley are anxiously 

 asked about its advance. When it is near 

 the town of Piura, parties go out to wel- 

 come it with music and fireworks, return- 

 ing with its trickling advance over the dry 

 sandy bed. Thousands greet its arrival at 

 the city. Excellent cotton is produced in 

 the valley, and the crop might be much ex- 

 tended by systematic irrigation ; but most 

 of the water in the rising river is allowed to 

 waste itself in the sea. Once in from five to 

 seven years rain falls on the plain ; then it 

 is soon covered with grass and flowers, and 



cattle wander out of the valleys for a time; 

 but in a few weeks all is barren again. 



LAKES IN THE SAHARA NEAR TIMBUKTU. 



The great northward curve of the Niger 

 carries its fertile flood plain into the border 

 of the Sahara, where Timbuktu stands near 

 the margin of the upland in a region of sand 

 dunes alternating with stunted forests. The 

 wet season comes with the equatorial rains 

 from June to August ; but high water in 

 the river is delayed until Januarj"-, as if de- 

 termined by rains about the more southern 

 head branches. The river then overflows 

 its broad flood plain, above which the vil- 

 lages stand on sand dunes. French occu- 

 pation has brought to light several lakes 

 that occupy depressions between spurs of 

 the desert upland, which rises in abrupt 

 rocky slopes a hundred meters above their 

 waters. The largest, Faguibine, is about 

 60 kilometers north of the river and west of 

 Timbuktu; it is 110 kilometers in length 

 and over 30 meters deep ; almost compar- 

 able, therefore, with Lake Chad. It is fed 

 bj' a flooded distributary of the Niger dur- 

 ing high water ; in the drj^ season a current 

 sets back again from the lake to the river. 

 Debo is a somewhat smaller lake, appa- 

 rently lying on the flat flood plain of the 

 great river, 120 kilometers southwest of 

 Timbuktu (Blnszet, La region de Tombouc- 

 tou, Bull. Soc. geogr. Paris, xvi., 1895, 375- 

 388). 



Unless gratuitouslj' explained by local 

 subsidence, Faguibene may perhaj)s be re- 

 garded as one of those lakes that stand in a 

 lateral valley near its junction with a main 

 valley along which a great river has been 

 actively building up a heavy flood plain. 



PHYSIOGRAPHY OF MONTENEGRO. 



A RECENT supplement to Petennami's Mit- 

 teilungen consists of ' Beitrage zur phj's- 

 ischen Geographie von Montenegro,' by K. 

 Hassert, jwivatdoeent in Leipzig, giving a 

 very serviceable account of this rugged and 



