MIGRATION AND FLIGHT. 91 



seven years, constantly observed our three species, many 

 of them remaining all the year, but their numbers much 

 diminished from spring to autumn, when they were 

 supposed to be absent, spending their summer in Eu- 

 rope. 



On looking at the map, it will be seen, that without 

 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 a 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 keej) over the 

 land as much as possible; but if the straightest course 

 were preferred, 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 Marti- 

 nique, 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 oppor- 

 tunities would occur of seeing their arrival or departure 

 in flocks, but, with the exception of straggling parties of 

 ten or twelve at a time, few have been fortunate enough 

 to see them either come or go; whence it has been in- 

 ferred, that they pursue their course at night. And 

 that this is the case we can give tolerably good evidence 



