"There's where you don't understand the science of storms," said the captain smiling. "In the northern hemisphere typhoons, cyclones, and hurricanes--they are all the same--whirl from left to right, that is, they turn like the hands of a watch, while in the southern hemisphere their motion is exactly the reverse. When we think we are in the sweep of a typhoon in these waters, we run with the wind on our starboard, or right hand, and that course will take us away from the centre. In the southern hemisphere we run with the wind on the port, or left hand, with the same result. But we'll go to dinner now and be happy, for the danger is over." [Illustration: COURSE OF A TYPHOON.] Just as they were rising from table they were suddenly called on deck by the announcement of a wreck. An American bark had been dismasted by the gale and lay helpless on the water; her captain wished to be taken in tow to the mouth of the Yang-tse-kiang, and after some minutes spent in making a bargain, the matter was arranged and a line passed out. "They were less fortunate than we," the Doctor remarked as they proceeded with their tow. [Illustration: CAUGHT NEAR THE STORM'S CENTRE.] "Yes," answered the captain, "the poor fellow was nearer the centre of the typhoon than we were. There'll be a job for the ship-carpenters and riggers at Shanghai; it's an ill wind that blows nobody any good." Frank was looking through the captain's glass at the persons who were moving about the deck of the bark. Suddenly he observed something and called out to his companions: "Look, look! here's a familiar face!" The Doctor took the glass and then handed it to Fred; the latter looked steadily for a minute or more before he had a satisfactory view, and then said: "It's our old friend, the Mystery!" CHAPTER XXIII. FIRST DAY IN CHINA. In due time they entered the waters of the great river of Northern China, the Yang-tse. They entered them long before they sighted land, as the vast quantities of earth brought down by the stream make a change in the color of the sea that can be readily distinguished a great distance from the coast. In this respect the Yang-tse is similar to the Mississippi, and the effect of the former on the Yellow Sea is like that of the latter on the Gulf of Mexico. The coast at the mouth of the Yang-tse is low and flat, and a ship is fairly in the entrance of the river before land can be seen. The bar can be passed by deep-draught vessels only at high water, and consequently it often becomes necessary for them to wait several hours for the favorable moment. This was the case with our friends, and they walked the deck with impatience during the delay. But at last all was ready, and they steamed onward in triumph, dropping their tow at Woosung, and waving a good-bye to "the Mystery," who had recognized them from the deck of the disabled bark. [Illustration: THE WOOSUNG RIVER.]