62 J. ^i. WALLER ON SAND. 



bility of it being, in part at least, brought down by rivers. And 

 this will at once lead us to consider whether that noble stream, the 

 Rhine, may not be one of the factors of supply. Descending from 

 the Alps in a strong and powerful current, generally turbid, but 

 particularly so after a season of storms on the breaking up of winter, 

 it has for ages poured forth its waters into the German Ocean. I know 

 nothing more imposing than the scene presented, when looking down 

 from the hills beyond Bonn upon the vast delta before you. It is 

 as level as the sea, and far on the horizon the city of Cologne is 

 detected only by the lofty towers of its cathedral, as if a ship 

 riding on the ocean. Its many mouths must each send forth, mixed 

 with its strong current — for it is not tidal — a mass of sand, repre- 

 sented doubtless by the dunes of Holland and Belgium, which have 

 been planted with Equisetum to tie together its instable substance. 

 The Alpine loess of Belgium is itself largely commingled with 

 quartzose sand of similar origin, making a large source of supply. 



Amongst other materials than quartz referred to, chalcedony is 

 the most common ; there is also a kind of conglomerate, of minute 

 parts, which polarize vividly, some fragments homogeneous in colour, 

 being of a neutral grey, as well as some other substance less easy to 

 describe, whilst in some few cases there are pieces evidently from 

 granitic rock. Flint, when seen under polarized light, does not 

 exhibit colour, but nevertheless its character is thus best distin- 

 guished. Occasionally I have imagined I have seen some instances 

 in which a change has been undergone. I speak of this doubtfully, 

 but certainly there is nothing which has the slightest approach to a 

 metamorphosis into quartz. It has been supposed by some that an 

 infiltration of chalcedony does take place occasionally, but that must 

 surely be, if at all, before the formation of sand particles. An old 

 French writer, M. Reaumur, in the " Memoires de FAcademie des 

 Sciences," 1721, writes : — tc By a coarse operation emery is reduced to 

 powder, and suspended in water several days ; but nature may go 

 much further than this, for the particles which water detaches from 

 hard stones by simple attrition are of an almost inconceivable 

 degree of fineness. Water thus impregnated contributes to the 

 formation of pebbles by petrifying the stone, as it were a second 

 time. Stones already formed, but having as yet a spongy texture, 

 acquire a flinty hardness by impregnation with this crystalline 

 fluid." 



I state this as I find it. The author gives no facts, so the hypo - 



