MIGRATION OF ANIMALS. 273 



M. Adanson, in his voyage, informs us, that, about fifty 

 leagues from the coast of Senegal, four swallows settled upon 

 the ship, on the sixth day of October ; that these birds were 

 taken ; and that he knew them to be the true swallows of Eu- 

 rope, which he conjectures were then returning to the coast 

 of Africa. Mr. Barrington,* with more probability, supposes 

 that these swallows, instead of being on their passage from 

 Europe, were only flitting from the Cape de Verde Islands to 

 the continent of Africa, a much shorter flight, but to which 

 they seemed to be unequal, as they were obliged, from fatigue, 

 to light upon the ship, and fall into the hands of the sailors. 



Swallows, Mr. Kalm remarks, appear in the Jerseys about 

 the beginning of April, and are, on the first arrival, wet, be- 

 cause they have just emerged from the sea or lakes, at the 

 bottom of which they had remained in a torpid state during 

 the whole winter. But Mr. Kalm, who wishes to support the 

 torpidity of swallows during the win'.er, likewise informs us 

 that he himself met with them at sea, nine hundred and twenty 

 miles from any land. 



These and similar facts, Mr. Barrington endeavors to ex- 

 plain, by supposing that birds discovered in such situations, 

 instead of attempting to cross large branches of the ocean, 

 have been forcibly driven from some coasts by storms, and 

 that they would naturally perch upon the first vessel which 

 came within their view. 



In Great Britain, five species of swallows appear 'in sum- 

 mer and disappear in winter. 1. The house-swallows make 

 their appearance about twenty days earlier than the martin, 

 or any other of the swallow tribe. They are often seen about 

 the 13th day of April. They disappear about the end of 

 September. A few days previous to their departure, they 

 assemble in great flocks on the tops of houses, churches, and 

 trees, from whence they are supposed to take their flight. 

 This unusual arid temporary association of numbers indicates 

 the impulse of some common instinct by which each individ- 

 ual is actuated. The house-swallow is easily distinguished 

 from the other species by the superior forkiness of its tail, 

 and by a red spot on the forehead, and under the chin. This 

 species builds in chimneys, and makes its nest of clay, but 

 leaves the top quite open. 2. The martin is inferior in size 

 to the former, and its tail is much less forked. The martins 



* Essay on the periodical appearing and disappearing of certain birds at different 

 times of the year. P/iil. Trans. Vol. LXII. 



