range of items that farmers use and that can be
preserved and shown. The variety nearly equals the volume. Most museums
try to avoid duplication. Even so, few museums manage to collect a
continuous series of things showing any one line of development. The
discontinuity of farm objects on hand virtually rules out the telling of
a coherent and complete history of agriculture. Nevertheless, the museum
can show something about the major technological developments in
agriculture. The evolution of the plow, the reaper, or the tractor can
be suggested even if not fully illustrated. Hitting the highlights has
to suffice.

The full history of technological change also involves several social
and economic conditions.

First, changes in implements, tools, and methods result from the
accumulation of knowledge. Device builds upon device: first came the
wheel, and then, much later, the tractor.

Secondly, the potential user of the device must feel a need for it. The
new method or device not only must save him work but must clearly
increase his well-being. If any device or change merely increases the
wealth of someone else (a tax collector or a landlord for example), the
farmer seldom will adopt the new technology.

Thirdly, since, at first, the new technology almost invariably costs
more than the old, the user must have or be able to get the capital to
buy and use the newer devices and methods.

Of these conditions for technological change, only the cumulative nature
of the knowledge can be shown by the objects. Even here, however,
missing objects make it possible to present only the most obvious
changes, and then not all of them. Still, seeing the things once
used--no matter how crude or how few--can sometimes help us understand
the way changes took place. Also, this knowledge sometimes can help us
guess how other changes will take place:

The sequence of inventions also depends upon the changing needs of
a society. Needs and circumstances vary more than do degrees of
talent. Thus when need and knowledge merge, inventors quickly
appear. Indeed, several men in several places are likely to work on
the same problems at the same time, and they often solve it in
almost identical fashion. Nearly simultaneous inventions or
discoveries occur with astonishing frequency in the history of
technology.[2]

[Footnote 2: "The Combine Made in Stockton," Pacific Historian, no. 10
(Autumn, 1966), p. 1