The rainy season of Tette differs a little from that of some of the other intertropical regions; the quantity of rain-fall being considerably less. It begins in November and ends in April. During our first season in that place, only a little over nineteen inches of rain fell. In an average year, and when the crops are good, the fall amounts to about thirty-five inches. On many days it does not rain at all, and rarely is it wet all day; some days have merely a passing shower, preceded and followed by hot sunshine; occasionally an interval of a week, or even a fortnight, passes without a drop of rain, and then the crops suffer from the sun. These partial droughts happen 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 degrees 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 degrees, rain might be expected; at Kolobeng, the point at which we looked for a storm was 96 degrees. 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 becomes 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.