d
become the greatest exporter of wheat in the world. The invention of the
twine-binder made this possible, making practicable the raising of greater
crops of wheat; for as Professor T. N. Carver says: "The _harvesting_ of
the grain crop is the crucial point. The farmer has to ask himself, not,
'How much grain can I grow?' but, 'How much can I harvest with such help
as I can get?'" By the late seventies the steam thresher was fast
supplanting horse-power and a great impetus was given wheat growing when
the roller process for manufacturing flour was invented. By this process
better flour was made from spring wheat than had ever been produced from
the winter grain, and this made Minneapolis the Flour City, in place of
Rochester.

In rapid succession the check-rower, permitting cross cultivation of
corn, the lister, for deep plowing and planting, the weeder, the riding
cultivator, the disk harrow and other kindred machines greatly helped the
production of corn, our greatest crop. Cheese and butter factories and
improvements in dairy methods helped to make Americans probably the
largest consumers of butter in the world. The Babcock test for determining
the butter fat, and the centrifugal separater for extracting the cream,
were most important.

_The Evolution of the Plow_

In the last quarter century the improvement on these earlier farm machines
has been remarkable and elaborate. One of the most wonderful continued
stories of human ingenuity is the evolution of the plow, from the historic
crooked stick that merely tickled the surface of the ground (and is still
used in many countries) to the steam gang-plow which tears up the earth at
an astonishing pace, and thoroughly prepares the soil meanwhile. When with
a gang-plow and five horses, it became possible for a man to plow five
acres a day, it was supposed the acme of progress was attained. But soon
steam traction was introduced on the prairies and two men were able thus
to plow a dozen furrows at once and cover thirty to forty acres in a day.

Now, however, a 110-horse power machine, a monster of titanic power and
expert skill, plows a strip thirty feet wide, as fast as a man could
comfortably walk, and also does the harrowing and sowing simultaneously.
This completes the work of plowing and planting at the rate of 80 to 100
acres in a working day, or under favorable conditions even twelve acres an
hour, thus doing the work of forty to fifty teams and men. Yet millio