100 Description of the Landes of Acquitania. 
On the coast of Flanders, between Ostend and Zealand, the 
downs are not more than 200 feet in thickness, forming a single 
ray of small hills; but this chain of downs attains a_ breadth of 
from five to six miles, its height diminishing in its progress from 
north to south, so much so, that at the lowest extremity the crest 
is not elevated above 12 to 15 feet. ‘The forms of the summits is 
dome-shaped, and sometimes more or less acute ; their outline is 
often serrated, and their slope mostly gentle and undulating. 
The sand of which the hills are constituted, consists of small 
grains of quartz, sometimes, but seldom, mixed with the detritus 
of shells. 
The ocean is supposed to deposit upon the coast a quantity of 
this sand, valued at 34.9383 feet, (10 metres 6.49 millimetres, ) 
for every 6.5618 feet (2 metres) in length, or 44,104,380 cubic 
feet, (1,245,405 cubic metres,) for the whole length of 766,132.61 
feet, (233,1513 metres,) at 5 toises 2 feet French for every pro- 
gressive toise, or 640,000 cubic toises for the whole length of 
120,000 toises from the northerly point to the mouth of the Adour. 
(Journal de Santé et d Hist. Nat. par Capelle, Bordeaux 1797.) 
From their extent and elevation, and from the continued level 
of the Landes, these hills are seen in the evening like streaks of 
snow for 30 miles round ; but when the air is heated, the refrac- 
tion increases their height, and their appearance becomes really. 
striking. 
It is in the Létes or deep vallies alone, that quicksands, known 
in these districts by the name of Bedouses, sometimes Blouses or 
Tremblans, are met with. It is a fact, with which every peasant 
is acquainted, that cattle are generally endowed with an instinctive 
perception to avoid them, and thus the traveller, when he cannot 
trust to his own caution, may follow their tracks. 
They originate generally from the accumulation of a small quan- 
tity of water becoming covered with sand, which, transported by 
the winds, falls like rain on their surface, ordinarily tranquil and 
sheltered. The sand remains in equilibrium, as it were, in the 
middle of the waters, forming an infinity of little vaulted supports ; 
these sustain others, and the last rise many feet above the waters, - 
the superior layers becoming white, and mingling with surround- 
ing sands, which forms a trap scarcely to be avoided by the most 
experienced. , 
They also sometimes originate from the support given to the 
sands by Nuphars, Potamogetons, Menyanthes, &c. from which the 
same appearances may result. In cases of accident, great: tran- 
quillity must be observed, and the sands, accumulating under the 
feet, will soon afford a firm support. 
The object which has given the most interest to the natural his- 
tory of downs, has been their progress inwards, and their well 
known power of burying, in their advance, the monuments of art, 
and the products of industry ; and wherever extensive downs oc- 
cur, too many proofs of such facts are constantly met with in: the 
