466 
Hints for the Formation of 
16. When the characters of a fossil give it such a like- 
ness to another that it is found near the limits which 
separate the genera or species of these two fossils, we must 
follow the example of Werner and his disciples, by mark- 
ing that this fossil is intermediary, or forms a transition, 
from the one species to the other. For if we should 
ascribe it exclusively to the genus A, without noting 
the characters which bring it near to the genus B, ano- 
ther observer, on seeing the same fossil, might refer it to 
the genus B, and no one could know which of them was 
deceived. 
17* People are often deceived also by mixing opinion 
with observation, and giving the former for the latter ; as 
when people assert, that they have seen vestiges of ex- 
tinguished volcanoes, because they have seen black or 
porous stones, or stones of a prismatic form, without 
deigning to describe them with care, but by qualifying 
them merely as lava or hasaltes. 
18. In the last place, a very frequent source of error is, 
too great a confidence in the fidelity of one’s memory, or 
in the justness of one’s first observations. These two kinds 
of confidence go often hand in hand ; and people cannot 
guard against the errors, which are the consequence of 
them, but by noting down, on the spot, all observations 
to which any importance is attached, especially if they 
are a little complex, and carry away specimens, with their 
characters carefully marked upon them, of the objects 
that are the subject of these observations ; for it is not spe- 
cimens of rare objects merely that should be collected. 
The end, indeed, of the geological observer is, not to form, 
a cabinet of curiosities, but lie must carry away fragments 
cupero's pyrites of JEtna. The errors of this kind, arising 1 from false denomina- 
tions, are innumerable ; for an exact knowledge of mineral substances is more 
difficult to be obtained, and more rare, than is generally imagined. — Note of the 
Author. 
