"Sure," answered Ned.  "The atmosphere surrounding the earth is just like the water in the large reservoirs--there are deep places and shallow places, holes you can drop in, and currents like the Gulf Stream current, the Japanese current, which warms the northern states and British Columbia, and the Arctic Humboldt current, which sends a cold stream down the Pacific coast of South America.  If we have no difficulties with these rivers of the air, and the wind does not come up too strong, we can make Asuncion by six o'clock in the morning.  It is about ten now."