Geology.] 
NATURAL HISTORY. 
023 
INSTRUCTIONS FOR COLLECTING GEOLOGICAL 
SPECIMENS. 
It so often happens that specimens sent from distant 
places, by persons unpractised in geology, fail to give the 
instruction which is intended, from the want of attention to 
a few necessary precautions, that the following directions 
may perhaps be useful to some of those, into whose hands 
these pages are likely to fall. It will be sufficient to pre- 
mise, that two of the principal objects of geological inquiry, 
are, to determine,— -1st, the nature of the materials of which 
the earth is composed; and, 2ndly, the relative Order in 
which these materials are disposed with respect to each 
other. 
1. Specimens of rocks ought not, in general, to be taken 
from loose pieces, but from large masses in their native place, 
or which have recently fallen from their natural situation. 
2. The specimens should consist of the stone unchanged 
by exposure to the elements, which sometimes alter the cha- 
racters to a considerable distance from the surface. — Petri- 
factions, however, are often best distinguishable in masses 
somewhat decomposed ; and are thus even rendered visible, 
in many cases, where no trace of any organized body can 
be discerned in the recent fracture. 
3. The specimens ought not to be too small. — A conve- 
nient size is about three inches square, and about three- 
quarters of an inch, or less, in thickness. 
4. It seldom happens that large masses, even of the same 
kind of rock, are uniform throughout any considerable space ; 
so that the general character is collected, by geologists who 
examine rocks in their native places, from the average of an 
