136 NORTH UIST. SAND. 



to mark their former connexion with some higher tract 

 of land, and to serve as a record of those changes which 

 have hollowed the sinuosities of that loch. I need not 

 enter on the probable causes of these changes, as they 

 have been often discussed, and as in describing the 

 island of Staffa, which exhibits a remarkable example 

 of this nature, eveiy thing is said which occurs on the 

 subject. I may only remark, that the alluvial matter 

 and the rolled stones which are seen in these islands, 

 are all equally the produce of the islands themselves, 

 no boulders of granite, except fragments of the granite 

 veins, being any where found among the substances scat- 

 tered over their surfaces. 



Having repeatedly mentioned the accumulations of sand 

 which occur on the western side of this tract of insular 

 land, and which are as prevalent in North Uist as in 

 the islands that lie to the south, it appears necessary 

 to describe more particularly their nature and progress, 

 as far as it is possible to decipher that progress, often 

 very obscure. This is a phenomenon with which geology 

 as well as agriculture is concerned, since these accumu- 

 lations, which tend at times to fertilize and at others to 

 overwhelm and destroy the soil, may also lay the founda- 

 tions of beds capable by future changes of being converted 

 into strata of marie, or, ultimately, even into limestone. 



The sand thus accumulated on the western shores of 

 this land, is formed for the most part of various com- 

 minuted shells, of which however only fragments can 

 be obtained ; insufficient to show the species from which 

 they have originated. Such shells in their living state 

 form beds, as the sounding line testifies, skirting the 

 eastern shore; fine shell sand as well as clay being also 

 found at different depths along the coast. In some places, 

 as in Barra and Vatersa, this sand seems to consist of 

 shells only, while in North Uist as well as in other parts, 

 a portion of quartz and hornblende, the result of the 

 wearing of the rocks, is mixed with the calcareous matter. 



It is not easy to perceive the exact mode in which the 



