s themselves are not easy to
define: not a little ingenuity has been expended on the attempt, and
perhaps the best brief classification that has been put forward is one
which divides labor into the following four grades:--

(1) Automatic manual labor.
(2) Responsible manual labor.
(3) Automatic brain workers.
(4) Responsible brain workers.

But the matter is one perhaps for the satirist of manners rather than
the economist. It suffices for our purpose that the distinctions,
however vague, are very real.

It is obvious the mobility of labor between the occupations of a
platelayer and a barrister is not very great. It may seem perhaps to
be even smaller than it is. For here it is important to bear in mind a
general consideration which is equally applicable to horizontal
movements within any social grade. There may be a considerable
movement of labor between different employments without any individual
worker having to change his occupation. The personnel of any industry
is constantly changing. At one end, men die, retire, or are pensioned
off; at the other end, young recruits are taken on. By a diversion of
the new recruits from one employment to another, a radical change can
be made in the occupational census in a comparatively short space of
time. It is in this manner that such movement as takes place is
largely effected at the present time. Within the ranks of the
professional classes, a man does not commonly leave the profession to
which he has been trained. But his _choice_ of profession is
determined by him or his parents not solely on pecuniary grounds but
usually with an anxious scanning of the general prospects, which
include pecuniary advantages together with many other things. The same
thing is true in no small measure of manual wage-earners. This general
consideration must be borne in mind throughout the remainder of this
chapter.

But even the sons of platelayers do not commonly practise at the
bar. The obstacles in the way are various and subtle. Many of them are
ideas, inherited from a bygone epoch, about keeping other people "in
their proper stations," which the whole drift of circumstance, and the
spirit of the age are rapidly wearing down. In the new world such
obstacles are rare. But an obstacle of a more tangible and formidable
kind arises from the fact that the liberal professions and many
business careers require a long and expensive education and training,
which the platelayer is quite unable