0基础编写松下PLC完整项目程序

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0基础编写松下PLC完整项目程序

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0基础编写松下PLC完整项目程序

Hungry and cold, he sat beneath the descending night, gazing down into the blackening void below. Presently, as the darkness deepened, he saw a light twinkling far below and then another and another and with each his excitement rose, for he knew that they marked the presence of man. In many places upon the marsh-like lake he saw the fires twinkling, and at a point which he took to mark the site of the island there were many lights.

What sort of men were they who tended these fires? Would he find them friendly or hostile? Were they but another tribe of African blacks, or could it be that the old legend was based upon truth and that far below him white men of The Lost Tribe cooked their evening meals above those tantalizing fires of mystery?

What was that? Von Harben strained his ears to catch the faint suggestion of a sound that arose out of the shadowy abyss below—a faint, thin sound that barely reached his ears, but he was sure that he could not be mistaken—the sound was the voices of men.

And now from out of the valley came the scream of a beast and again a roar that rumbled upward like distant thunder. To the music of these sounds, von Harben finally succumbed to exhaustion; sleep for the moment offering him relief from cold and hunger.

When morning came he gathered wood from the stunted trees near by and built a fire to warm himself. He had no food, nor all the previous day since he had reached the summit had he seen any sign of a living creature other than the game a mile beneath him on the verdant meadows of the canyon bottom.

He knew that he must have food and have it soon and food lay but a mile away in one direction. If he sought to circle the canyon in search of an easier avenue of descent, he knew that he might not find one in the hundred miles or more that he must travel. Of course he might turn back. He was sure that he could reach the base of the outer slopes of the Wiramwazi, where he knew that game might be found before exhaustion overcame him, but he had no mind to turn back and the thought of failure was only a vague suggestion that scarcely ever rose above the threshold of his conscious mind.

Having warmed himself before the fire, he turned to examine the fissure by the full light of day. As he stood upon its brink he could see that it extended downward for several hundred feet, but there it disappeared. However, he was by no means sure that it ended, since it was not a vertical cleft, but tilted slightly from the perpendicular.

From where he stood he could see that there were places in the fissure where descent would be just possible, though it might be very difficult to reascend. He knew, therefore, that should he reach the bottom of the fissure and find that further descent was impossible he would be caught in a trap from which there might be no escape.

Although he felt as fit and strong as ever, he realized perfectly that the contrary was the fact and that his strength must be ebbing and that it would continue to ebb still more rapidly the longer that he was forced to expend it in arduous efforts to descend the cliff and without any possibility of rebuilding it with food.