NOTES ON COLLECTING MINERALS. 
133 
one who has given special attention to the study of mineralogy and 
geology, and has himself collected the specimens : rock-specimens 
collected here and there, and without correlative information as to . 
the geological structure of the district, are rarely worth the trouble 
and expense of transport. But if trouble and expense are to be left 
entirely out of account, a traveller in a region which is comparatively 
unknown, or which contains neither mines nor quarries, may occa- 
sionally be of service by collecting material representative of the 
rocks met with during his journey. 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 various 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 
2 pounds' weight is sufficient. Strong chisels, 4 or 5 inches long, are 
also occasionally useful. A small trimming-hammer, from | 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 
