506 THE TROPICAL WORLD. 



* always as active and raerry as ever ; and upon opening their chambers the walls were 

 invariably moist. la reply to the question, whence these insects derived their water, 

 Livingstone suggests that they have the power by vital force of combining the oxygen 

 of the air with the hydrogen of their food, and so making water. He instances, in 

 support of this theory, other insects which he found in Angola, where a colony of in- 

 sects on the branch of a tree would distill several pints of water in a single night ; 

 and he satisfied himself, by cutting off the branch, and so stopping the flow of sap, that 

 this water was not derived from the juices of the tree. But in this case the atmosphere 

 was surcharged with moisture ; while in the Kalahari it was so dry that the best 

 hygrometrie tests at his disposal failed to detect moisture in the air. A needle exposed 

 for months in the open air did not rust ; there was no dew on the ground, and a mix- 

 ture of sulphuric acid and water parted with all its water to the air, instead of imbib- 

 ing more from it, as it usually does. We know of no facts to confirm Livingstone's 

 theory of this insect manufacture of water. Our theory is that the ants went down 

 far enough to find water in the soil. Paradoxical as it may seem, the extraordinary 

 heat — 132° to 134° at a depth of three inches — and the absolute dryness of the air, 

 would diminish the distance before moisture was reached ; for the surface would soon 

 be baked so as to be as hard as sandstone, thus precluding evaporation from any con- 

 siderable depth, by forming a solid crust through which no water could escape. He 

 dug wells deep into the bed of the dried-up river near by, but found no water. We 

 imagine that if he had followed Solomon's injunction to " go to the ant and be wise," 

 and dug down close by one of their habitations, he would have come to moist sand 

 at no great depth; and this moisture would, by natural laws, have flowed into his 

 well. 



The human inhabitants of this wide African semi-desert are of very varied character. 

 A large portion of them, Caffres, Bechuanas, and the like, belong to the lowest grade 

 of humanity, perhaps a little above the aborigines of Australia, and some tribes in 

 Borneo, which, could we admit of any connecting link between men and monkeys, we 

 would designate as semi-human. There are other tribes, such as the Balakahari, which 

 rise far higher in the scale of being ; and are, we judge, quite susceptible of civiliza- 

 tion. They have garden patches which they cultivate with great care, and rear small 

 herds of goats, although they are often in the dry season obliged to dip up for them 

 water absolutely in spoonfuls. They are also keen traders in their small way, barter- 

 ing the skins of animals for spears, knives, tobacco, and dogs. These tribes merge 

 almost imperceptibly into the Makalaka and Mak^lolo, whom Livingstone found in 

 the more favorable region to the North, around Lake Ngami. 



There is also in Africa another vast region which belongs apparently to the savannas 

 rather than to what we consider the proper tropical regions. For want of a better 

 term we may designate it as the " Lake Region," for in it lie great lakes, inferior only 

 to those of North America, whose very existence was until within a few years unknown 

 to the civilized world. Geographically it is purely equatorial, for it lies within five 

 degrees of the equator on either side ; and its elevation is not such as of itself suffi- 

 cient to greatly modify its climate ; but other circumstances give it an aspect wholly 

 unexpected. In general it may be described as a plateau of 3,000 to 4,000 feet 

 above the ocean, with little outcropping hills of granite, and many fertilizing springs 



