20$ Hints for the Formation of 
or not ; or? in other words, whether the branches of that 
trunk are opposite or alternate ? 
The answers to these two questions are vefy impor- 
tant for the solution of this question : Whether the val- 
leys have been excavated by currents of the sea? 
9. Whether there are seen a great number of narrow 
valleys, of no great depth at their most elevhted part, but 
becoming wider and deeper in proportion as they de- 
scend lower, which would seem to indicate that their ex- 
cavation has been the effect of the fall and descent of 
water ; especially if the strata have the same inclination 
on each side of the valley, and if its formation cannot 
be explained by a sinking down or heaving up of the 
earth. 
10. To observe in a valley, the corresponding moun- 
tains of which are of the same nature, whether the strata 
of these mountains do not descend on each side towards 
the bottom of the valley, which would indicate that the 
valley has been produced by a sinking down of the earth, 
or perhaps by the opposite faces being thrown up. 
11. There are two other cases possible when the stra- 
ta have not the same situation on both sides of the val- 
ley. 1. When the strata rise up on each side against 
the valley. 2. When on one side they descend into the 
valley, and on the other rise against it. These two cases 
afford room for suppositions too various to be here de- 
tailed. 
12. To search on the vertical sides of the valleys for 
vestiges of the erosion of the water. 
13. To observe the bottom of the valley, its breadth, 
inclination, and nature. The vegetable earth, its quan- 
tity and quality; fragments, either from neighbouring 
mountains, or brought from a distance, either angular or 
rounded ; to examine whether they are more voluminous 
towards the top of the valley. Nature and depth of the 
