SPECIFIC GRAVITY OF SAND. 93 



and watering, or the culture, produces or attracts, of appropriate 

 nutriment of plants. 



The drift sand, strictly speaking, though variegated by a sprinkling 

 of somewhat rare grains of darker coloured substances, is a mass of 

 a light colour. Amongst the lightest coloured is the washed out sand 

 of the north, whicli is of a gi'eyish white. Amongst the darkest is the 

 drift sand of the Bannat in Hungary, covered with a strong mould 

 containing iron, which is of a yellowish light brown. In a wet 

 state all drift sands are of a dark hue. So far as the surface is 

 acquiring or has acquired a covering of vegetation of some years 

 standing, it appears of a dai'ker colour, varying with the kind of 

 plant, with the richness of the vegetation in humus, and with the 

 age of this, varying, for example, from a light grey brown to a 

 black brown hue. 



Many drift sands have also an admixture of a coarser form of 

 sand, which on sea strand dunes is as large as pearls, and in inland 

 situations goes indefinitely beyond this : round pieces, even to the 

 size of blocks ; concretions of lime of the most varied forms ; shells of 

 snails and of mussels ; cemented clods ; and the whole layer is hardened 

 like stone. These larger sized materials are altogether absent in the 

 wind-raised dunes. Such is the European drift sand in general. In 

 individual cases, however, the character varies with the district, 

 the origin and the thickness of the layer, and the transformations 

 occasioned by geological changes, by vegetation, &c. 



He reports the specific gravity of the different constituents, which, 

 with the exception of the humus, which, on the authority of experi- 

 ments by Schueblei*, recorded in his Agricultur-Chemie, he gives as 

 1-370, ranges from 2-468 to 2-722; and he shows that the differences 

 between 1-370 and 2-468 of specific gravity in sands, may be attri- 

 buted to varying quantities of humus or products of vegetable decay 

 in their composition. 



As the result of numerous detailed experiments cited in an 

 appendix embracing the composition of sands existing in numerous 

 parts of Germany and Austria, he gives the specific gravity of the 

 sands of North Germany as 2-5-2-9 ; average, 2-7 ; of the sands of 

 Hungary, as 2-1-2-65 ; average, 2-5 : attributing the greater weight 

 of the former to the smaller quantity of lime, and the greater 

 quantity of iron-ore, and mica in their composition. And, for 

 comparison, he gives, on the authority of M. Schuebler, the specific 

 gravity of arable land generally as 2-401, and of garden ground as 

 2-332 ; and on the authority of Hauer, that of the celebrated fields 

 of Banat as 1-8-2-5 ; average, 1-18. 



