"I can't tell you, my boy," Mr Harvey said. "That everything, even the tzetze has a good purpose, you may be sure, even though it is hidden from us. Possibly, for example, it may be discovered some day that the tzetze is an invaluable medicine for some disease to which man is subject, just as blistering powder is obtained from the crest-body of the cantharides beetle. However, we must be content to take it on trust. We must leave our descendants something to discover, you know, Dick; for if we go on inventing and discovering as we are doing, it is clear that they must look out for fresh channels for research." CHAPTER THIRTEEN. A BRUSH WITH THE NATIVES. One day Jumbo touched Dick's arm, as he was riding along with the caravan, and, pointing to a clump of trees at some little distance, said,-- "Giraffe." Dick reined in his horse, and gazed at the trees. "I don't see it," he said. "They are very difficult to see," Mr Harvey remarked; "they have a knack somehow of standing so as to look like a part of the tree. I don't see him myself, but if Jumbo says he is there, you may be sure he is." "Is the skin valuable?" Dick asked. "No, Dick, it would not be worth cumbering ourselves with. Nor is the flesh very good to eat--I do not say it cannot be eaten, but we have plenty of venison. I never like shooting a giraffe when I can help it. Clumsy and awkward as they are, they have wonderfully soft and expressive eyes, and I do not know anything more piteous than the look of a dying giraffe; however, if you ride up to the trees and set them scampering, you will get a good laugh, for their run is as awkward and clumsy as that of any living creature." Dick accordingly started at a gallop towards the trees; it was not until he was close to them that he saw three giraffes, two old ones and a young one. They started off, as he approached, at a pace which seemed to Dick to be slow, as well as extraordinarily clumsy. The two old ones kept themselves between their offspring and the pursuer, as if to shield it from a shot. Dick, however, had no idea of firing; he only wished to gallop up close, so as to get a nearer view of these singular beasts, but to his astonishment he found that, although his horse was going at its best speed, the apparently slow-moving giraffes were steadily gaining upon him. He could hardly at first believe his eyes. But he was gradually tailed off, and at last, reining in his horse, he sat in the saddle and enjoyed a good laugh at the strange trio in front of him, with their long, straggling legs and necks. When he rejoined the caravan Mr Harvey, who had watched the pursuit, asked him laughingly if he managed to catch the giraffe. "I might as soon have tried to catch an express train; they went right away from me,--and Tommy can gallop too; but he hadn't a chance with them, although he did his best."