Here, he exercised the greatest caution. It was possible that a sentinel had been posted on the crest-line. He accordingly advanced by way of a donga, which led to the hill-top, and in which he could not be seen. When he cleared the donga, a few yards from the crest, he went down on hands and knees, and crawled from boulder to boulder.

A few minutes later, he found himself looking down upon the settlement of Makanda. He was immediately above the kraal, and from that altitude he was able to see inside the enclosure. The kraal consisted of four rows of huts. In one of these was a white figure which, even without the aid of his glasses, he had no difficulty in recognizing as one of the Arabs. This man, rifle in hand, entered a hut, and presently came out with a party of six slaves, all of whom wore iron collars around their necks, which were fastened together by a single chain. Followed by the Arab, this party left the kraal, and turned to the left, towards the southern extremity of the lake.

Max directed his field-glasses upon the stockade. He could see no one therein but Cæsar's Arab cook, who was walking leisurely from the direction of the river with a bucket of water in either hand.

By now the slave-driver and his party were out of sight to the south. Max, anxious to observe whatsoever was in progress, descended from the sky-line and ran in all haste along the ridge. He soon came to a place whence he was able to see the course of the river, which had taken a sudden bend to the west above the lake, where it was spanned by a rope suspension bridge, such as is often met with in the heart of Africa. Beyond the bridge, the sight that he witnessed held him rooted to the spot.

He beheld a large quarry, where about fifty natives were at work. In charge of these were four Arabs, and Max had no difficulty in distinguishing Cæsar and the half-caste de Costa.

The work which was in progress was singular, by reason of the fact that this was Equatorial Africa where, at that time, commerce, industry and enterprise were quite unknown. A group of slaves in charge of the Portuguese himself, was gathered together beneath the walls of the quarry. A little distance from them was a great heap of rubbish. Suddenly, the whole party was seen to set off running in the direction of the river. Cæsar was the last to retire.

There followed a tremendous explosion. A great column of dust and smoke was thrown up into the air. And even before this had descended, or had been carried away upon the wind, both Cæsar and the natives had hastened back to the place, where there was now a great rent in the living rock. There they set to work carrying baskets of débris to de Costa, who supervised a party engaged in sifting. Now and then, something was taken from the siftings and handed to de Costa, who examined it, and cast it into a wheelbarrow. At intervals, this wheelbarrow was taken to a third party at the water's edge that was engaged in washing something in pans.

Max was, at first, too interested and surprised at all this to take notice of an occurrence in the nature of a tragedy which was taking place farther up the stream. There, about a dozen natives lay stretched at full length upon the sand at the water's edge. Some of these lay still and motionless, as if in death; others were writhing in agony; from time to time one would endeavour to raise himself, but invariably fell back, drawing up his knees as if in fearful pain.

Even at that distance, Max could not fail to recognize the symptoms of cholera--the most severe and fatal of all diseases. At various intervals in the history of the world, cholera has raged in Asia and throughout the eastern parts of Europe. In the early part of the nineteenth century a violent outbreak occurred in Bengal, which in a short time spread throughout the length and breadth of India. Thence, it raged eastward into China, and westward through Persia and Turkey to Russia and Central Europe. North Africa was also afflicted, and the valley of the Nile, whence the pestilence had evidently now crossed to the basin of the Congo.

No disease in the world is more deadly and virulent. It strikes down its victims swiftly and without warning. Even as the men worked at the quarry, Max observed one who took himself a little distance from his fellows, and sat down upon a rock as though he were in pain.