MIGRATION AND FLIGHT. 107 



diminished from spring to autumn, when they were 

 supposed to be absent spending their summer in 

 Europe. 



On looking at the map, it will be seen, that with- 

 out further peril by sea, than simply crossing the 

 short space of the British Channel and Straits of 

 Gibraltar, (either of which, at their narrowest parts, 

 even a barn-fed Sparrow might easily do in an hour 

 or two,) a bird might make almost a direct course to 

 Sierra Leone, a distance of about 3000 miles, which 

 space a Swallow would, without effort, traverse in 

 three days, including time for roosting at night, and 

 which even the Sparrow could perform at leisure, 

 and without the least fatigue, in less than a fortnight. 

 The above calculation is made on the supposition 

 that the airy travellers keep over the land as much 

 as possible ; but, if the straightest course was pre- 

 ferred, they might, by crossing the Bay of Biscay, 

 perform it in less time. And that Swallows do, at 

 least occasionally, take this line, we know, from the 

 very curious fact of one settling on the rigging, and 

 caught on board a vessel bound to the French port of 

 Havre, beneath the wing of which was found a very 

 small slip of paper, on which was written, in French, 

 " The ship Armide, Captain Borgnet, going to Mar- 

 tinique, latitude 48 33' north, longitude 10 39' 

 west." On reference to the map, it will be seen 

 that this point is nearly in a straight line, drawn 

 from the Land's End in England, to the western 

 coast of Africa. 



It might be supposed, taking place as these 

 journeys do with Swallows twice in the year, that 

 frequent opportunities would occur of seeing their 



