384 Notes and Memoranda. 



source of tlie Great Nile, and that the Bahari-lSTgo, which supplies 

 the Tubiri, is the Eastern, I haye little doubt. But the Arcanum 

 Magnum of Old World geography has not yet been solved. It still 

 remains to this generation, as to its forefathers, " Caput quserere 

 ISTili" — to close the canon of geographical discovery. 



Dr. Livingstone wished to explain the use of the words Nyanza 

 and Nyassa.; both meant simply a piece of water. He had adopted 

 "Nyassa" as the name of the Southern Great Lake, which he had 

 explored, not because it was especially distinguished as such by the 

 natives, but because it was convenient to give it a definite name. 

 Last year he endeavoured to reach the northern end of this lake, to 

 ascertain whether or not a large river entered it from the north, but 

 was prevented from doing so by the hostility of a colony of Zulu 

 Caffres there established. But he saw and heard enough to satisfy 

 him that no great river entered at that point. Fifteen miles to the 

 west of Nyassa stretched a high tract of table-land from which 

 flowed numerous rivers, and one of these, after passing through 

 two laites, was said to enter Lake Tanganyika ; but all this part of 

 Africa still remained to be discovered. He saw no difficulty in a 

 new expedition reaching this region, if they pushed quickly from 

 the unhealthy low lands of the coast to the high lands, the explo- 

 ration of which would soon decide the question of the water- shed of 

 Central Africa. 



Mr. Galton thought that the theory of a northern outlet to 

 Lake Tanganyika had much to recommend it. The low altitude of 

 1844 feet, as taken by Captains Burton and Speke, need offer no 

 difficulty, for the only instrument which they used was a common 

 shilling thermometer. He did not think Captain Burton quite so 

 fortunate in his theory about Victoria RTyanza not been continuous 

 from Ukerewe to the Bipon Falls. 



NOTES AND MEMOBANDA. 



The Magnesium Light. — Cosmos states that the apparatus for burning mag- 

 nesium wire, contrived by Mr. Grant and improved by M. Leroux, involves an 

 expenditure of thirty centimes (about 3d.) per minute, reckoning magnesium at the 

 price of If. 20c. the gramme (15 , 432 grains). An ordinary photographic negative 

 can be taken with its aid in 30 seconds, and an enlarged imago obtained in from 

 two to three minutes ; and the writer reckons that even if three or four magnesium 

 lights are employed, the expense would still be less than that of the electric light. 

 Can this be correct with regard to the cheaper forms of electric light ? For 

 theatrical purposes he thinks magnesium will be valuable for brilliant illumina- 

 tions of short duration, but that when they are required to last for a quarter of an 

 hour the electric light will be cheaper. 



Arctic and Alpine Vegetation. — A certain amount of success attends the 

 comparison of the vegetation at given elevations, and at corresponding varia- 

 tions in latitude ; but the distribution of heat is very different under the two 

 conditions. Upon a mountain top in France or Switzerland the solar rays tra- 

 verse a clear thin air, and strike vigorously upon the soil, which they heat con- 

 siderably ; while in such a neighbourhood as that of Spitsbergen the dense air 

 intercepts a great deal of solar heat. From these facts we shall not be surprised 



