satisfactory. It may be the beginning of the acquaintance, but you are
hardly, in your thoughts, advanced towards science, whatever the
subject may be."

It has now become possible to measure exactly the elements which enter
into nearly all physical phenomena, and these measurements are taken
with ever increasing precision. Every time a chapter in science
progresses, science shows itself more exacting; it perfects its means
of investigation, it demands more and more exactitude, and one of the
most striking features of modern physics is this constant care for
strictness and clearness in experimentation.

A veritable science of measurement has thus been constituted which
extends over all parts of the domain of physics. This science has its
rules and its methods; it points out the best processes of
calculation, and teaches the method of correctly estimating errors and
taking account of them. It has perfected the processes of experiment,
co-ordinated a large number of results, and made possible the
unification of standards. It is thanks to it that the system of
measurements unanimously adopted by physicists has been formed.

At the present day we designate more peculiarly by the name of
metrology that part of the science of measurements which devotes
itself specially to the determining of the prototypes representing the
fundamental units of dimension and mass, and of the standards of the
first order which are derived from them. If all measurable quantities,
as was long thought possible, could be reduced to the magnitudes of
mechanics, metrology would thus be occupied with the essential
elements entering into all phenomena, and might legitimately claim the
highest rank in science. But even when we suppose that some magnitudes