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.
In August, which is one of the "hurricane months" of the tropics, when the _Josephine_ left Grenada on her voyage to England, the winds are more variable, blowing at odd and uncertain times; so, there was every reason for Captain Miles' taking advantage of the first cat's-paw of air off the land now, as otherwise, perhaps, he might not have been able to make an offing before morning, when he would lose the advantage of the current amongst the islands towards Saint Vincent, where he had to call in for some puncheons of rum and coffee to complete his cargo.
Under the direction of Moggridge, the crew made short work of hoisting in my traps and innumerable boxes, including the cocoa-nuts Doctor Martin had sent down for me, all of which Captain Miles ordered to be taken into the cabin he allotted to me on the starboard side of the ship near his own; and then, the boat itself was hauled on board by the derrick amidships which had been used for getting in the cargo, there being no davits at the side as in a man-of-war.
After seeing this operation satisfactorily accomplished, I went up the poop-ladder and walked aft to the side of Captain Miles, who was now busy about getting the vessel under weigh.
"Hands up anchor!" he roared out with a stentorian shout, and immediately there was a bustle forward of the men with much thumping of their feet on the planks and a clanking of the chain as the windlass went round under their sturdy hands.

Mr Marline, the first mate, I noticed, had charge of the crew engaged in heaving, while Moggridge went on the forecastle to see that everything was clear for catting and fishing the anchor as soon as it was run up out of the water and the stock showed itself above the bows.
"Clink, clank! clink, clank!" came the measured rattle as the slack of the cable was wound round the windlass and carried along the deck to the chain locker; and then, after another spell of hard heaving, Moggridge sang out, "Swings clear, sir!" "All right," responded Captain Miles, jumping up on a hen-coop by the taffrail so as to make his voice go further, as well as to command a clear view of all that was going on, "Hands, make sail!" On hearing this order those of the crew who were not engaged at the windlass swarmed up the rigging and threw off the gaskets of the foresail and mainsail, while a couple of hands ran out on the bowsprit and unloosed the lashings of the jib, the topsails having been dropped before I came on board.
"Man the topsail halliards!" then sang out the captain, and with a cheery cry the yards were run up with a will and the halliards then belayed.
"Sheet home!" was the next command, whereupon the sails were stretched out to their full extent, swelling out before the off-shore wind; and one of the men, by the captain's orders, now going to the helm, a few turns of the spokes brought the vessel's head round.
"Now, look alive there forward and heave up the anchor!" shouted Captain Miles.
In another minute the stock of the kedge showed above the bows, when the catfalls being stretched along the deck, and laid hold of by Moggridge, the rest of the crew tacking on after him, the flukes were run up to the cat-head to a rhythmical chorus in which all hands joined, the men pulling with a will as they yelled out the refrain-- "Yankee John, storm along! Hooray, hooray, my hearties! Pull away, heave away, Hooray, hooray, my hearties! Going to leave Grenada!" The clew-garnet blocks now rattled as the main-sheet was hauled aft, when, the broad sail filling, the _Josephine_ paid off before the wind; and shortly afterwards she was making her way to leeward towards Saint Vincent, passing almost within a stone's throw of Fort Saint George, as she cleared the northern point of the harbour and got out to sea.
The jib and flying-jib were now hoisted as well as the topgallant-sails and spanker, to get as much of the breeze as we could while it lasted, so that the vessel began to make fair progress through the water; and the hands under the superintendence of the two mates were then set to work coiling down ropes and getting in the slack of the sheets as well as making things ship-shape amidships, where the deck was still littered with a good deal of cargo that had not yet been properly stowed.
I was all this time standing by the side of Captain Miles on the poop, alternately looking at the men jumping about the rigging like monkeys and at the fast-receding shore, which, as soon as the sun set, became dimmer and dimmer in the distance, until it was at length finally shut out from my gaze by a wall of mist.
"Fo'c's'le ahoy, there!" sang out Captain Miles presently, when it began to grow dusk.
"Aye, aye, sir!" responded the voice of Moggridge, the boatswain, from forward.
"Keep a good look out, my man, ahead, or we may be running down some of those coasting craft inward bound." "Aye, aye, sir, I'm on the watch myself," sang out Moggridge; but hardly had he given this answer than, all at once, he cried out suddenly in a louder tone, "Hard a-port, hard a-port! There's something standing across our bows." The man at the wheel immediately put the helm up, letting the head of the vessel fall off from the wind; but, at the same instant, there came a sudden crash ahead, followed by a loud yell.
"Gracious heavens!" cried out Captain Miles, rushing forwards to the forecastle, where several of the hands had also hurried on hearing the cry of the boatswain--I going after the captain in my turn to see what was the matter, dreading some fearful disaster.
There were several short and quick exclamations, amidst which I saw, in the dim light, Moggridge in the act of heaving a rope overboard towards some dark object in the water.
"Hooray, he's got it and has clutched hold!" I then heard somebody say.
"The line has fallen just over his shoulders, and he has got the bight of it." "Haul him in gently!" cried the captain.

"Pull easy--so!" Next I saw a couple of the seamen bending over the side, and in another moment they helped a dripping figure to scramble on to the deck; when, as I pressed nearer to see who the rescued person was, I heard a well- known voice exclaim, in tones of earnest thankfulness and joy: "Bress de Lor', I'se safe!" It was Jake, the very last person in the world, most certainly, whom I could have expected to meet on board the _Josephine_, if I had guessed a hundred times!.