sis of the process of making lumber, or in other
words absorption and reflection. In the observation of such a complex
piece of machinery as a large mill the mind swings back and forth many
times between absorption in the study of parts and reflection upon
their relation to each other.

Having examined the mill in detail and grasped its parts as a connected
whole, the next step is to observe its relation to the river, to the
rafts and rafting-boats, and further back to the pineries and
logging-camps up the river. (Northern Minnesota and Wisconsin.) The
occupations and sights along the Upper Mississippi and its head-waters,
the pineries, and even the spring floods, are intimately connected,
causally, with the saw-mills and lumber yards lower down. Or going in
the opposite direction from the saw-mill, we follow the lumber till it
is used in the various forms of construction. Some of it enters the
planing-mills and is converted into moldings, finishing lumber, sashes,
blinds, etc. In all forms it is loaded upon the cars, and shipped
westward to be used in the construction of houses and bridges.

Before we get through with the line of thought engendered by observing
the saw-mill, we have canvassed the whole lumber industry from the
pineries to the plans of architects and builders in the actual work of
construction. Not only has there been this progress of the mind from
one object or machine to another of a _series_ connected by cause and
effect, but there has been also a constant tendency to pass from the
individual machines of which the series is composed to the classes of
which these objects are typical. A circular-saw or a gang-saw is each
typical of a class of saws. The same is true of each part of the
machinery, as well as of the saw-mill or planing-mill considered as a
whole. Each of these objects, whether simple or complex, suggests
others similar which we have observed or seen represented in pictures.
Each part of the machinery in turn becomes the center of a set of
comparisons leading from the concrete object in question to the general
notion of the class to which it belongs. For example, the steam engine
in a mill is typical of all stationary engines used for driving
machinery. But the parts of the engine are also typical of similar
parts in other engines and machines, as the drive-wheel, cylinder,
boiler, etc.

In all these cases we become absorbed in one thing for a while, only to
recover ourselve