MEANS OF DISPERSAL. 153 



when carried to great heights, Mr. Wallace observes, 

 may occasionally be drifted off by strong upper currents 

 and dropped at great distances, " and with them small 

 insects and mollusca or their eggs." ^ 



''On 27th July, 1875, a remarkable shower of small 

 pieces of hay occurred at Monkstown, near Dublin. 

 They appeared floating slowly down from a great 

 height, as if falling from a dark cloud which hung over- 

 head. The pieces picked up were wet, and varied from 

 single blades of grass to tufts weighing one or two 

 ounces. A similar shower occurred a few days earlier 

 in Denbighshire, and was observed to travel in a direc- 

 tion contrary to that of the wind in the lower atmo- 

 sphere." ■' 



From what distances the hay had come in these 

 cases no one can tell ; it was, however, in a position 

 to be conveyed, as Mr. Wallace remarks, to almost 

 any distance by a violent wind, had such occurred at the 

 time ; doubtless it was originally taken up by whirl- 

 winds, and this was the case also, in all probability, with 

 the leaves which fell in Dumfriesshire in 1889. Slight 

 whirlwinds, according to Lyell, may frequently be 

 observed in our fields, in summer, carrying up haycocks 

 into the air, and then letting fall small tufts of hay far 

 and wide over the country ; - the Irish whirlwind of 

 1872 as just noted carried a large quantity of hay into 



^ " Island Life," p. 274, ed. 2, p. 285. 



^ Wallace, "Darwinism," ed. 2, (1889), p. 362 ; quoting " Nature/' 

 xii. (187s), pp. 279. 298. 

 3 " Principles," ii. p. 392. 



