When the force reached the mouth of the river, it was too late to begin the work of constructing canoes. Tom ordered his men to make an entrenched camp, and to throw up a special earthwork behind the screen of reeds, where a company of picked marksmen could easily defend the canoe-makers from attack. Early next morning Tom set all his men who had axes to fell the largest and straightest teak in the forest, a few hundred feet from the shore. When the trees were felled, another band of men was set to strip off the foliage and bark, and so quickly did they work that by nightfall a large number of huge logs lay ready for scooping out, varying in length from forty to sixty-five feet. Tom saw that he would need a fleet of about forty-five canoes if he intended to convey all his force to the island at one time, as would probably be necessary. He therefore selected the requisite number of trees himself, and while the carriers were felling these he instructed the warriors how to dig them out. He divided them into gangs of twenty to thirty, each gang to form one canoe crew, and he set these to fashion their own craft. He marked off equal lengths along the logs, and gave each man his own portion to scoop out with knife or pike-head, encouraging them to work hard by the promise of a reward to the man who finished his portion first. They all worked with a will, driving their tools into the wood with unfaltering zeal, and showing much interest in their novel work.
While the digging-out was in progress, Tom employed other men in making thwarts and rough paddles, and the best carpenters in constructing scaling-ladders. After ten days' work he was in possession of forty-five dug-outs, with their due equipment of paddles, and fifty ladders ten feet high. The canoes were, of course, keelless, and Tom knew that they were bound to sway and roll with the slightest movement of the body; but fortunately there was little likelihood of their having to encounter rough weather, and he hoped that they would suffice to convey his men across the four miles separating the lake shore at this point from the island. "They'll do as well as Napoleon's flat-bottom boats, I expect," he thought; "or better, for his invasion never came off, and mine will."
The work had not been carried on for ten days without molestation. Every day canoes came from the island, filled with armed men, evidently curious to learn what was going on out of sight. On the first day they paddled towards the mouth of the river, and Tom ordered his men behind the earthwork to allow them to approach well within gunshot, and then to let them have a sharp volley. The canoes came within fifty yards of the concealed marksmen without suspecting their danger, and at least half the men on board were hit when the Bahima opened fire. The survivors paddled away in frantic haste, and ever after that the canoes kept out of harm's way, the Arabs contenting themselves with patrolling the lake, in cheerful assurance that their fortress was impregnable. All this time Tom sent scouting-parties regularly along the shore, from whom he learnt that at several points on the western side there were large clearings, which appeared to have been slave settlements, and he concluded that the slaves had either been withdrawn into the island or sent deeper into the forest.
His preparations so far being complete--and none too soon, for the stock of food was running low,--Tom decided to make a reconnaissance towards the island. He first tested some of his canoes on the river, out of sight from the Arabs, employing a few men who knew how to paddle, and found to his great pleasure that, though clumsy and incapable of being propelled swiftly, they rode the water fairly upright, and were safe enough in a calm. He therefore ordered his men to launch half a dozen of the canoes at the mouth of the river, and with these fully manned with riflemen he moved slowly towards the island. The movement was instantly observed; hardly a minute had elapsed before a fleet of twenty light, swift canoes, filled with armed Manyema, shot out from the island and made towards him. Recognizing that he could not hope to vie with them in speed, and that he could not approach the island so closely as he wished without running great risks, Tom ordered his men to paddle back, and regained his camp. A tremendous yell of delight from the Arabs' canoes, ringing clear over the still water, bore witness to the enemy's confidence, but Tom only smiled. He remembered reading, in one of Stanley's books, an account of how that great explorer had defended some canoes from attack in precisely similar circumstances, and once more he found his recollection serve him well. He sent his men into the forest, some to cut long poles an inch thick, others to cut poles three inches thick and seven feet long, a third band to cut straight long trees four inches thick, and a fourth to remove the bark from all these and make bark-rope. While this was being done Tom selected three of the longest canoes, and had them drawn up parallel to one another near the water's edge, and four feet apart. As the stripped trees were brought up they were laid across the canoes, and lashed firmly to the thwarts with the bark-rope. Then the seven-foot poles were lashed in an upright position to the thwarts of the outer canoes at the extreme edge, and the inch-thick rods were twisted in and out among these uprights, just as gipsies make baskets. After this, thin saplings were woven in through any remaining interstices, and at the end of the day the structure resembled a huge oblong stockade of basket-work, sixty-five feet long and twenty-seven feet wide. A gap having been cut in one of its faces, and a rough gate made, the contrivance was complete.
Next morning Tom went to a distance of three hundred yards and tried a shot at the stockade with one of his men's rifles. The bullet penetrated the wall, but fell dead inside. He then ordered his men to collect reeds and large leaves from the toughest plants they could find, and with these to line the inside of the palisade. When this was done he tried another shot, and found that the bullet embedded itself in the lining. Delighted with the assurance that the structure was practically bullet-proof, he next instructed his men to make loopholes at intervals along the sides, and then ordered eight hundred of the carriers to haul and push the strange, awkward-looking fort to the water. He then sent sixty paddlers to take their places on the thwarts, and a hundred and fifty musketeers to find room among them. He was in some anxiety lest with its full complement of men the fort should be too heavy to float, but a few moments' paddling convinced him that, unwieldy as it was, it would ride the water, though to propel it with any speed was out of the question. A great shout of applause burst from the onlookers as the floating fort moved a few yards towards the lake. Tom ordered it back, stepped on board, closed the gate, and started on his reconnaissance.
The warriors left on shore watched the progress of the strange craft across the lake. It went on slowly and steadily towards the island, and reached the middle of the channel before any sign of movement was made by the enemy. Then forty canoes swept out swiftly from the island's green bank, and in one of the foremost, as it came more clearly in sight, Tom, spying through one of the loopholes, saw his old enemy De Castro. The canoes came on rapidly; when within four hundred yards they stopped dead, and the men on board of them opened fire. The worst marksman could hardly have missed so huge a target, and the exposed wall of the redoubt rang with the impact of hundreds of bullets, only a few of which penetrated, to fall quite harmlessly in the water between the canoes. Tom then ordered the paddlers to slew the fort round, so that it presented one of its longer sides to the enemy, and a few moments later a volley burst from the loopholes, doing considerable damage among the crowded craft of the Arabs. Seeing that the inventiveness of the English lad had once more proved too much for him, De Castro, with a curse, ordered his men to paddle back to the island, and Tom was left to make his reconnaissance unmolested.
Slowly the unwieldy mass moved round the island--slowly, steadily, like some uncouth leviathan. Even Tom's own men on shore, who had seen it made, watched it with awe, and some of them cried out that it was a spirit in monstrous shape. As he circumnavigated the island, Tom kept a keen look-out towards it, and found that there were several possible landing-places, the shore being comparatively low. Deciding that the most convenient point of debarkation was a sparsely wooded tongue of land at the south-east corner, Tom made a careful mental note of the whole position, and returned to his own quarters, well satisfied with his day's work.
The next two days were spent in constructing two similar floating redoubts, and in practising the men in paddling, for the majority of them were helpless on the water. Tom was loth to delay his attack, and feared that De Castro might make an attempt to escape. He therefore withdrew half the men from the block-house at the edge of the forest, and kept them, along with men from his force, constantly patrolling the shores of the lake, to watch for any movement from the island. His fears were groundless, as he afterwards discovered. De Castro did indeed suggest to Mustapha that the principal men should decamp with the treasure, leaving the fort to its fate, but the Arab curtly refused. He had sworn an oath on the Koran before Rumaliza's departure to defend the treasure till the last, and he himself had a bone to pick with the audacious English youth who had tied him up with his own rope in his own hut. He was, besides, so positive that the enemy, even if he effected a landing, would fling himself in vain against the defences, that he scoffed at De Castro's fears and taunted him with cowardice.
At dawn on a bright January day Tom set forth on his momentous enterprise. The three redoubts, each with two hundred men on board, led the way, followed by thirty canoes fully manned, these last containing the worst marksmen in the force. Tom half expected that the enemy, having already proved their helplessness against the floating forts, would make no attempt to oppose his landing; but he soon saw that his passage was not to be uncontested. Forty-five canoes came out to meet him. At a distance of a thousand yards the Arabs' flotilla divided into two squadrons, and, rowing three strokes to the one of Tom's paddlers, evidently intended to sweep behind the cumbrous redoubts and fall upon the canoes, a design which Tom at once took steps to defeat. He was himself in the centre redoubt. He ordered the other two to move off to right and left until there was a clear quarter of a mile between him and them. The formation of his flotilla had then roughly the shape of a bent bow, the three redoubts representing the arc and the canoes the angle formed by the stretched string. By thus extending his front, Tom compelled the Arabs to make a wide circuit. Even then they passed within range of the loopholed faces of the floating forts, and suffered severely from the merciless volleys poured out by the Bahima. Drawing out of range, they had just begun to converge behind the redoubts when Tom ordered these to stop, thus allowing time for his canoes behind to close up and pass between them. The position was now reversed, the bow being pointed in exactly the opposite direction, Tom's canoes nearest the island, and the Arabs' farthest away. Within his redoubt Tom could distinctly hear the wild threats and cries of De Castro as he ordered his men to swing round and paddle back to the island.
"He's afraid we shall be there first," said Tom with a smile to Mbutu.