58 COLL. GENERAL DESCRIPTION. 



sands, afford against their violence. It is not long 

 since the utility of these plants has been known to the 

 natives, and it is with some difficulty that they are even 

 now restrained by the more enlightened proprietors 

 throughout the islands from destroying them, and thus 

 accelerating the progress of this wasting inundation. The 

 use of the Galium verum as a dye, is the chief inducement 

 to this pernicious practice. The sand consists in a great 

 measure of broken shells, mixed, however, with the quartz 

 which arises from the decomposition of the gneiss. 

 Being thrown on the shore by the prevalence of the 

 western swell, it is dried by the winds and dispersed by a 

 gradual progress into the more inland parts. Thus, in 

 particular places, and in proportion to the obstacles it 

 encounters, it forms banks and sand hills ; or else is dif- 

 fused bver the flatter tracts, where the renewal of vegeta- 

 tion tends to consolidate and retain it, thus perma- 

 nently raising their level. In other situations it pro- 

 duces a soil on the naked rocks, accumulating in their 

 sheltered interstices and forming a basis for a vegetation 

 to be ultimately extended ; while it operates as a constant 

 manure to the peaty tracts within its reach, loosening the 

 tenacious soil and promoting the vegetation of white 

 clover and other useful plants, in place of the scanty 

 covering of rushes and useless vegetables with which they 

 were before encumbered. Thus, like manures, it is 

 injurious only by excess, and in recording its devasta- 

 tions, it is but justice to describe its beneficial properties*. 

 The plants which cover the sandy plains of Tirey 



* To the other advantages derived from the sand inundation it may 

 be added, that it often produces valuable and permanent additions to 

 the extent of the islands exposed to its influence. A great part of Tirey 

 appears to be of no very distant origin, having been formed by its 

 accumulation on a ledge of low rocks extending between the hills that 

 occupy the extremities of this island. The traditions which record the 

 recent existence of salt water inundations in its central parts confirm 

 this opinion. 



