86 THE HARMONIES OF NATURE. 



through considerable spaces in a very short time during ordi- 

 nary tempests ; for strong gales, which can sweep along grains of 

 sand, often move at the rate of about forty miles an hour. The 

 hurricanes of tropical regions, which root up trees and throw 

 down buildings, may carry even the heavier fruits and seeds 

 over friths and seas of considerable width, and doubtless are 

 often the means of introducing into islands the vegetation of 

 adjoining continents. 



Whirlwinds are also instrumental in bearing along heavy 

 vegetable substances to considerable distances. Slight ones 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 ; but they are sometimes so power- 

 ful as to dry up lakes and ponds, and to break off the 

 boughs of trees and carry them up in a whirling column of air. 

 As this cause operates at different intervals of time throughout 

 a great portion of the earth's surface, it may be the means of 

 bearing not only plants but animals to points which they could 

 never otherwise have reached, and from which they may then 

 begin to propagate themselves again as from a new centre. 



The long downy filaments which are appended to the numer- 

 ous seeds of the Gossypias, or cotton-plants, deserve particular 

 notice, as they not only waft them easily through the air, but 

 serve also to clothe a large portion of the human race, and rank 

 as the very first of all the world-wide importations of England. 

 Liverpool arid Manchester, with their train of minor stars, un- 

 doubtedly the scene of the most gigantic industry known in 

 the history of man, owe their prosperity to the wings with which 

 Providence has furnished the seeds of a small and otherwise 

 unimportant family of plants. 



Some seeds are dispersed by the sudden springing open of 

 the elastic capsule in which they are contained. In this manner 

 the seeds of the Balsam balsamine are jerked to a considerable 

 distance, and the Ura crepitans, an Indian shrub, accompanies 

 this action with an exploding noise which has been compared 

 with that of a pistol shot. 



In the dispersion of seeds, rivers and marine currents arenot less 

 instrumental than the atmospherical agencies. The mountain- 

 stream or torrent washes down to the valley the seeds which 

 may accidentally fall into it, or which it may happen to sweep 



