Chap. II. SEASONS AT TETTE. 45 



in December and January. The heat appears to increase 

 to a certain point in the different latitudes so as to 

 necessitate a change, by some law similar to that which 

 regulates the intense cold in other countries. After several 

 days of progressive heat here, on the hottest of which the 

 thermometer probably reaches 103° in the shade, a break 

 occurs in the weather, and a thunderstorm cools the air 

 for a time. At Kuruman, when the thermometer stood 

 above 84°, rain might be expected ; at Kolobeng, the point 

 at which we looked for a storm was 96°. The Zambesi is 

 in flood twice in the course of the year ; the first flood, a 

 partial one, attains its greatest height about the end of 

 December or beginning of January ; the second, and 

 greatest, occurs after the river inundates the interior, in a 

 manner similar to the overflow of the Nile, this rise not 

 taking place at Tette until March. The Portuguese say 

 that the greatest height which the March floods attain is 

 thirty feet at Tette, and this happens only about every 

 fourth year ; their observations, however, have never been 

 very accurate on anything but ivory, and they have in 

 this case trusted to memory alone. The only fluviometer 

 at Tette, or anywhere else on the river, was set up at our 

 suggestion ; and the first flood was at its greatest height 

 of thirteen feet six inches on the 17th January, 1859, and 

 then gradually fell a few feet, until succeeded by the 

 greater flood of March. The river rises suddenly, the 

 water is highly discoloured and impure, and there is a 

 four-knot current in many places ; but in a day or two 

 after the first rush of waters is passed, the current be- 

 comes more equally spread over the whole bed of the 

 river, and resumes its usual rate in the channel, although 

 continuing in flood. The Zambesi water at other times is 

 almost chemically pure, and the photographer would find 

 that it is nearly as good as distilled water for the nitrate 

 of silver bath. 



