EAKTHQUAKES. 



13 



The principal cause of disease during the summer of 

 Unyamwezi is the east wind, which, refrigerated by the 

 damp alluvial valleys of the first region and the tree- 

 clad peaks and swampy plains of Usagara, sweeps the 

 country, like the tramontanas of Italy, with a freezing 

 cold in the midst of an atmosphere properly tepid. 

 These unnatural combinations of extremes, causing 

 sudden chills when the skin perspires, bring on in- 

 evitable disease ; strangers often suffer severely, and the 

 influenza is as much feared in Unyamwezi as in England. 

 The east wind is even more dangerous in the hut than 

 in the field : draughts from the four quarters play upon 

 the patient, making one side of the body tremble with 

 cold, whilst the other, defended by the wall or heated 

 by the fire, burns with fever-glow. The gales are most 

 violent immediately after the cessation of the rains ; 

 about the beginning of August they become warmer 

 and fall light. At this time frequent whirlwinds sweep 

 from the sun-parched land clouds of a fine and pene- 

 trating clay-dust, and slight shocks of earthquakes are 

 by no means uncommon. Three were observed by the 

 Expedition — at noon on the 14th of June, 1858 ; on the 

 morning of the 13th of June; and at 5 p.m. on the 22nd 

 of November, 1858. The motion, though mild, was 

 distinctly perceptible; unfortunately, means of ascer- 

 taining the direction were wanted. The people of the 

 country call this phenomenon " Tetemeka," or the 

 trembling; and the Arabs remember a shock of a 

 serious nature which took place at Unyanyembe in the 

 hot season of 1852. After September, though the land 

 is parched with drought, the trees begin to put forth 

 their leaves ; it is the coupling season of beasts, and the 

 period of nidification and incubation for birds. The 

 gradual lowering of the temperature, caused by the 



