194 Hints for the Formation of 
their months are situated. M. Besson even wishes that 
the traveller should be furnished with a wooden vessel 
( sebille J to wash the sand and separate the more pon- 
derous particles, which may consist of metal or precious 
stones. The motion of the waves is also often sufficient 
to separate, in distinct bands or zones, particles of difi 
ferent gravity.* 
8. Nature of the rolled pebbles found on their borders. 
9« The quantity and kinds of fish by which they are 
characterised. 
10. To inquire, as in regard to the sea, whether it 
appears that they contain more or less water than for- 
merly, and whether they have changed their courses. 
11. As the greater part of these qnestions may be ap- 
plied to lakes, it is not necessary to make them the sub- 
ject of a separate chapter. I shall insist only on their 
nature and the measure of their depth ; on the tempera- 
ture of their bottom compared with that at their surface 
in different seasons ; and also on the vestiges of their ex- 
tent and height in the remotest ages, compared with their 
present state. 
CHAP. VII. 
Observations to be made on the Plains . 
1. The extent, limits, and inclination of a plain ; its 
height above the level of the sea ; its relaton with the 
hills or mountains by which it is bordered. To form a 
proper idea of it as a whole, it would be necessary to 
ascend some eminence commanding a view over it. 
The vegetable earth ; its nature and thickness in 
different parts, compared with the time since it has been 
* Moyens de rendre utiles les voyages des nat'uralistes. Esprit dgs Jour- 
imux, Avril s 1794„ 
