Science. DR. LENZ ON THE SAHARA.

Waikato Times, Volume XIX, Issue 1595, 23 September 1882, Page 6

Science. DR . LENZ ON THE SAHARA.

Dn. Oscaii Lenz gives in the last number of the Zeihchrlft of the Berlin Geographical Society (2) an accouut of the results of his journey across the Sahara, from Tanger to Timbuktu, and thence to Senegambia. The following good abridgement of his paper we take from Nature : " The real journey was begun at Marrakesh, at the northern foot of the Atlas mountains, where Dr. Lonz laid in his store of provisions and changed his name and dress, travelling further under the disguise of a Turkish Military surgeon. He crossed the Atlas and the Anti-Atlas in a southwestern direction. The Atlas consists, first, of a series of low hills belonging to the Tertiary and Cretaceous formations, then of a wide plateau of red sandstone, probably Triassic, and of the chief range, which consi&ts of clay-slates ■with extensive iron oies. The pass of Bibanan is 1250 metres above the sea-level, and it is surrounded with peaks about 4000 metres high, whilst the Wad Bus valley at its foot is but 150 metres above the sea. The Anti-Atlas consists of Palreozoic strata. On May 5, 1880, Dr. Lenz reached Tenduf, a small town founded some thirty years ago, and promising to acquire great importance as a station for caravans. The northern part of the Sahara is a plateau 400 metres high, consisting of horizontal Devonian strata which contain numerous fossils. On May 15 Dr. Lena crossed the moving sand-dunes of Igidi, a wide tract where ha observed the interesting phenomenon of musicalsand, a sound like that of a trumpet being produced by the friction of the small grains of quartz. But amidst these moving dunes it is not uncommon to find some grazing places for camels, as well as flocks of gazelles and antelopes. At El Eglab Dr. Lenz found granite and porphyry, and was fortunate enough to have rain. Thence the character of the desert becomes more varied, the route crossing sometimes sandy and sometimes stony tracts or sand-dunes, with several dry river bods running east and west between them. On May 29 he reached the salt works of Taudeni and visited the ruins of a very ancient town where numerous stone implements have been found. Hero he crossed a depression of the desert only 145 to 170 metres high, while the remainder of the desert usually reaches as much as 250 to 300 metres above the sea level; and he remarks that throughout his journey he did not meet with depressions below the sea-level. The schemes for flooding the Sahaia are therefore hopeless and misleading. The landscape remained the same until the wide Alfa fields which extend north of Arauan. This little town is situated amidst sand-dunes devoid of vegetation, owing to the hot southern winds. Four days later Dr. Lenz was in Timbuktu, whence he proproceeded west to St. Louis. During his forty-three days' travel through the Sahara Dr. Lenz observed that the temperature was not excessive; it usually was from 34 deg. to 36 deg. Celsius, and only in the Igidi region it reached 15 deg. The wind blew mostly from north-west, and it was only south of Taudeni that the tiaveller experienced the hot south winds [edrash] of the desert. As to the theory of north-eastern trade winds being the cause of the formation of the desert, Dr. Lenfc remarks that he never observed such a wind,* nor did his men; it' must be stopped by the hilly tracts of the north. " Another important remaik of Dr. Lenz is what he makes with respect to the frequent description of the Sahara as a sea-bed. Of course it was under the sea, but duxing the Devonian, Cretaceous and Tertiary periods; as to the sand which covers it now, it has nothing to do with the sea; it is the product of the destruction of sandstones by atmospheric agencies. Noithern Africa was not always a desert, and the cause of its being so now must be sought for, not in geological but in meterological influences."