1 5 6 



The Scottish Naturalist. 



Isle of Wight he found water-worn or rounded particles increas- 

 ing to one-fifth, while in Sussex and Kent they rose to from 

 one-third to one-half. Assuming the bulk of the sand on the 

 south coast of England to' be derived from the kaolin deposits of 

 Cornwall, the gradual transference of the sand up the English 

 Channel will account for the particles being more rounded the 

 further up they are from their place of origin. 



Looking at granite, its composition, and the results of its disin- 

 tegration, we may reasonably conclude that it has furnished a 

 large part of the sand found on the shores, sandy plains and 

 desert places of the earth. 



Besides granite, gneiss and mica-schist have a fair claim to 

 be regarded as contributing to the supply of sand. The same 

 influences that have operated in the disintegration of granite have 

 been at work on them, the quartz grains resulting from these 

 rocks being smaller. A specimen of garnet-sand, which I found 

 on the shores of Loch Tay, affords a striking proof of the effects 

 of the disintegration of mica-schist in producing particles of sand. 



Further, crystallized quartz is common in veins and drusy 

 cavities of rocks in all the different formations or systems ; and 

 by its disintegration, we can obtain another source of sand. 

 Besides, there is the natural formation of quartz-crystals from 

 silica, found in beds of clay. In the Royal School of Mines 

 there are some crystals of quartz, of theoretically correct form, 

 about -j- of an inch long. The pyramidal ends, or terminals, 

 being perfect show that they have not been found in attachment 

 to any rock substance as are most quartz crystals. They were 

 found, if I recollect aright, in blue clay. Dr. Sorby mentions 

 that he found crystallized sand of this kind in the boulder clay 

 near Scarborough ; and he accounts for the quartz crystals in 

 the sand of the beach at Scarborough being more perfect than 

 he found elsewhere by their being protected in clay. 



The shells of infusoria are often composed of silica and have 

 been found inclosing very minute quartz crystals. Their broken 

 shells and the spicula of certain sponges may be regarded as 

 contributing their share to the finer descriptions of silicious sands. 

 When the numberless multitudes of these minute organisms are 

 considered, their contribution will not be lightly estimated. 



Space will not permit one to do more than barely mention 

 volcanic eruptions and hot springs as supplying their quota in the 



