GEOGRAPHICAL DISTRIBUTION 335 



as thick as the flakes of snow in the heaviest snowstorm, and ex- 

 tended upward as far as could be seen with a telescope. During 

 two or three days they slowly careered round and round in an 

 immense ellipse, at least five or six miles in diameter, and at 

 night alighted on the taller trees, which were completely coated 

 with them. They then disappeared over the sea, as suddenly as 

 they had appeared, and have not since visited the island. Now, 

 in parts of Natal it is believed by some farmers, though on in- 

 sufficient evidence, that injurious seeds are introduced into their 

 grass-land in the dung left by the great flights of locusts which 

 often visit that country. In consequence of this belief Mr. Weale 

 sent me in a letter a small packet of the dried pellets, out of which 

 I extracted under the microscope several seeds, and raised from 

 them seven grass plants, belonging to two species, of two genera. 

 Hence a swarm of locusts, such as that which visited Madeira, 

 might readily be the means of introducing several kinds of plants 

 into an island lying far from the mainland. 



Although the beaks and feet of birds are generally clean, earth 

 sometimes adheres to them: in one case I removed sixty-one 

 grains, and in another case twenty-two grains of dry argillaceous 

 earth from the foot of a partridge, and in the earth there was a 

 pebble as large as the seed of a vetch. Here is a better case: the 

 leg of a woodcock was sent to me by a friend, with a little cake of 

 dry earth attached to the shank, weighing only nine grains; and 

 this contained a seed of the toad-rush (Juncus bufonius) which 

 germinated and flowered. Mr. Swaysland, of Brighton, who dur- 

 ing the last forty years has paid close attention to our migratory 

 birds, informs me that he has often shot wagtails (Motacillae), 

 wheatears, and whinchats (Saxicolae), on their first arrival on our 

 shores, before they had alighted ; and he has several times noticed 

 little cakes of earth attached to their feet. Many facts could be 

 given showing how generally soil is charged with seeds. For in- 

 stance. Professor Newton sent me the leg of a red-legged partridge 

 (Caccabis rufa) which had been wounded and could not fly, with 

 a ball of hard earth adhering to it, and weighing six and a half 

 ounces. The earth had been kept for three years, but when 

 broken, watered and placed under a bell glass, no less than eighty- 

 two plants sprung from it: these consisted of twelve monocotyle- 

 dons, including the common oat, and at least one kind of grass, 

 and of seventy dicotyledons, which consisted, judging from the 

 young leaves, of at least three distinct species. With such facts 

 before us, can we doubt that the many birds which are annually 

 blown by gales across great spaces of ocean, and which annually 



