labor.
It requires a deal of conscientiousness to take enough samples and
to take them thoroughly. The engineer does not exist who, upon
completion of this task, considers that he has got too many, and
most wish that they had taken more.

The accuracy of sampling as a method of determining the value of
standing ore is a factor of the number of samples taken. The average,
for example, of separate samples from each square inch would be
more accurate than those from each alternate square inch. However,
the accumulated knowledge and experience as to the distribution
of metals through ore has determined approximately the manner of
taking such samples, and the least number which will still by the
law of averages secure a degree of accuracy commensurate with the
other factors of estimation.

As metals are distributed through ore-bodies of fissure origin
with most regularity on lines parallel to the strike and dip, an
equal portion of ore from every point along cross-sections at right
angles to the strike will represent fairly well the average values
for a certain distance along the strike either side of these
cross-sections. In massive deposits, sample sections are taken
in all directions. The intervals at which sample sections must
be cut is obviously dependent upon the general character of the
deposit. If the values are well distributed, a longer interval
may be employed than in one subject to marked fluctuations. As
a general rule, five feet is the distance most accepted. This,
in cases of regular distribution of values, may be stretched to
ten feet, or in reverse may be diminished to two or three feet.

The width of ore which may be included for one sample is dependent
not only upon the width of the deposit, but also upon its character.
Where the ore is wider than the necessary stoping width, the sample
should be regulated so as to show the possible locus of values.
The metal contents may be, and often are, particularly in deposits
of the impregnation or replacement type, greater along some streak
in the ore-body, and this difference may be such as to make it
desirable to stope only a portion of the total thickness. For deposits
narrower than the necessary stoping width the full breadth of ore
should be included in one sample, because usually the whole of
the deposit will require to be broken.

In order that a payable section may not possibly be diluted with
material unnecessary to mine, if the deposit is over four