Another subject that occupied him was the natural history of the country.  He would account for desert tracts like Kalahari by the fact that the east and southeast winds, laden with moisture from the Indian Ocean, get cooled over the coast ranges of mountains, and having discharged their vapor there had no spare moisture to deposit over the regions that for want of it became deserts.  The geology of Southern Africa was peculiar; the geographical series described in books was not to be found here, for, as Sir Roderick Murchison had shown, the great submarine depressions and elevations that had so greatly affected the other continents during the secondary, tertiary, and more recent periods, had not affected Africa.  It had preserved its terrestrial conditions during a long period, unaffected by any changes save those dependent on atmospheric influences.  There was also a peculiarity in prehistoric Africa—­it had no stone period; at least no flint weapons had been found, and the familiarity and skill of the natives with the manufacture of iron seemed to indicate that they had used iron weapons from the first.

The travelers had got as far as the river Loangwa (of Nyassa), when a halt had to be called.  Some of the natives had been ill, and indeed one had died in the comparatively cold climate of the highlands.  But nothing would have hindered Livingstone from working his way round the head of the lake if only time had been on his side.  But time was inexorably against him; the orders from Government were strict.  He must get the “Pioneer” down to the sea while the river was in flood.  A month or six weeks would have enabled him to finish his researches, but he could not run the risk.  It would have been otherwise had he foreseen that when he got to the ship he would be detained two months waiting for the rising of the river.  On their way back, they took a nearer cut, but found the villages all deserted.  The reeds along the banks of the lake were crowded with fugitives.  “In passing mile after mile, marked with the sad proofs that ’man’s inhumanity to man makes countless thousands mourn,’ one experiences an overpowering sense of helplessness to alleviate human woe, and breathes a silent prayer to the Almighty to hasten the good time coming when ’man to man, the world o’er, shall brothers be for all that.’” Near a village called Bangwe they were pursued by a body of Mazitu, who retired when they came within ear-shot.  This little adventure seemed to give rise to the report that Dr. Livingstone had been murdered by the Makololo, which reached England, and created no small alarm.  Referring to the report in his jocular way, in a letter to his friend Mr. Fitch, he says, “A report of my having been murdered at the lake has been very industriously circulated by the Portuguese.  Don’t become so pale on getting a letter from a dead man.”