“Happening to go ashore one charming afternoon to purchase some milk at a house that stood near the river, and while talking with the people within doors, I was suddenly struck with astonishment at a loud rushing roar, succeeded by instant darkness, which for the first moment I took for a tornado about to overwhelm the house, and every thing around, in destruction.  The people observing my surprise, coolly said, ’It is only the pigeons,’ and on running out, I beheld a flock thirty or forty yards in width, sweeping along very low between the house and the mountain or height that formed the second bank of the river.  These continued crossing for more than a quarter of an hour, and at length varied their bearing, so as to pass over the mountain, behind which they disappeared before the rear came up.”

“That is amazing, Uncle Thomas; two thousand millions of live birds!  I can scarcely form an adequate idea of such a mass of living creatures.”

“There is something almost overwhelming in the idea, Frank; and yet in some parts of the world are to be found flocks of animals hardly less surprisingly numerous, when we consider how much less they are fitted for moving about, travelling at stated intervals from the mountains to the sea coast, and returning again to their old habitations, after having fulfilled the purposes for which this instinctive feeling was implanted in them.”

“Which animals do you mean, Uncle Thomas?”

“I allude to the land-crab, which is a native of the Bahamas, and also of most of the other islands between the tropics.  They live in clefts of the rocks, or holes which they dig for themselves among the mountains, and subsist on vegetables.  About the months of April and May, they descend to the sea coast in a body of millions at a time, for the purpose of depositing their spawn.  They march in a direct line towards their destination, and seldom turn out of their way, even should they encounter a wall or a house, but boldly attempt to scale it.  If, however, they arrive at a river, they wind along the course of the stream, and thus reach the sea.

“In their procession they are as regular as an army under the command of an experienced general, and are usually divided into three battalions.  The first body consists of the strongest males, which march forward to clear the route and face the greatest dangers.  The main body is composed of females, which are formed into columns, sometimes extending fifty or sixty yards in breadth and three miles in depth.  Three or four days after these follows the third division or rear guard, a straggling undisciplined tribe, consisting both of males and females, but neither so robust nor so vigorous as the former.