INSTRUCTIONS FOR COLLECTING ROCKS AND MINERALS. 203 
the geological structure of the district, are rarely worth the trouble 
and expense of transport. But any traveller in a comparatively 
unknown region, like the Antarctic, even though it contains neither 
mines nor quarries, may be of service by collecting material represen- 
tative of all exposed rocks met with during his journeys. Such 
material should be taken, not from the margin of the rock which has 
been long exposed to the action of the weather and is more or less 
altered, but from the inner part showing uniformity of character. To 
break off such specimens, the traveller should provide himself with a 
hammer of which head and shaft are reasonably proof against fracture. 
“Mineralogical hammers” are articles of commerce, and are of vari- 
ous weights and sizes ; the head is of well-tempered steel, one end of 
it being flat and square with an edge about 1 inch long, the other end 
having the shape of a chisel, the chisel-edge, also about 1 inch in 
length, being at right angles to the shaft: for most purposes a 
hammer of two pounds weight is sufficient. Strong chisels, 4 or 5 
inches long, are also occasionally useful. A small trimming-hammer, 
from 4 to } pound in weight, is convenient for use in the reduction 
of specimens to a proper shape and size. The size adopted for the 
specimen must depend largely on the sizes of the individual mineral 
constituents of the rock, since the specimen is to illustrate the 
average characters of the mass, and also on the conveniences for 
transport: a good average size, if the specimens are intended for 
exhibition, is, length 4 inches, breadth 3 inches, thickness from } to 1 
inch. As rock-material is very heavy, the reduction in size should 
be made at the place itself; another piece of the rock can then be 
immediately got, if by any mischance the specimen be spoiled in the 
course of the trimming. Where a rock shows variations of character, 
specimens should be selected in illustration thereof. 
The interest of a rock-specimen lies very largely in the relations 
of the mass of which it is a part to the other rock-masses in the 
district ; unless information as to the locality of the mass to which 
the specimen belonged is preserved, the specimen itself generally 
becomes valueless; for this and other reasons water-worn pebbles 
are not worthy of transport. Hence it is important to specify as 
precisely as possible the place from which each specimen has been 
broken, and also to take precautions against the possibility of a 
subsequent confusion of the localities of the specimens. A gummed 
label should be fastened on each specimen immediately after it has 
been trimmed, and a number should be written thereon referring to 
a corresponding entry in a note-book in which all the memoranda 
relative to the locality and the specimen are recorded: among these 
