These words put me on my mettle, so I picked up a bit and waved my handkerchief to dad, whom I could see standing still gazing after me; and, when the boat got alongside the vessel, I clambered up the side- ladder instead of allowing myself to be hoisted in as before. "That's your sort," said Moggridge, who followed me up closely, in order that he might catch me should I tumble back. He also helped me into the entry port and on to the deck of the _Josephine_, where I found Captain Miles waiting to receive me. "Ha, here you are at last, youngster!" he cried out in welcome. "I thought you were never coming out, and that we would have to start without you. Wind and tide, you know, wait for neither man or boy! Hoist in his traps, boatswain," he added to Moggridge, "and be as sharp as you can about it too, for the breeze is just beginning to come off the land." I may here mention a meteorological fact that Captain Miles subsequently explained to me. He said that this regular alternation of the sea and land breeze in warm latitudes, as in the tropics generally, when the wind blows for so many hours in the day on and off-shore, is owing to the different powers for the radiation and absorption of heat possessed by land and water, so that when the day temperature is highest on the land the alternating breezes will be stronger, and _vice versa_. During the day, to illustrate this fact, the radiation of the sun's heat on the land causes the air to expand and so rise from the surface, which, creating a vacuum, the air from the sea rushes in to fill the void. At night this process is reversed, for, while the surface of the soil will frequently show in the West Indies during the daytime a temperature of a hundred and twenty degrees and more under the meridian sun, the thermometer will sink down in the evening to fifty or sixty degrees; whereas, the sea, being a bad radiator and its temperature rarely exceeding eighty degrees, even at the hottest period of the day, it is alternately colder and warmer than the land, and the direction of the wind accordingly oscillates between the two. The minimum temperature being at a little before sunrise in the early morning and the maximum somewhere about two o'clock in the afternoon, the change of these breezes usually occurs at some little time after these hours, the one lulling and the other setting in in due rotation--that is, of course, near the coast, for out in the open sea their effect is not so apparent.