view of the fact that if the doctrine of mechanical
equivalents were applied to his claim, then the fundamental device on
which he improved would probably infringe upon it, which would be an
absurdity. It is thus seen that the pioneer inventor may have a claim
so broad in its terms that its terms cannot be escaped; that he may
invoke the doctrine of equivalents and have his claim dominate
structures not directly responding to the terms of the claim; that the
secondary inventor, who improves only the means, is limited to the
recited means and cannot invoke the doctrine of equivalents. But
within this general view, sight is not to be lost of the fact that
secondary inventors may be pioneers within certain limits. They are
not the first to produce the broad ultimate result, but they may be
pioneers in radically improving interior or sub-results, and they may
thus reasonably ask for the application of the doctrine of equivalents
to their claims within proper limits. The matter often becomes quite
complicated, for it is sometimes difficult to determine as to what is
the result in a given machine, for many machines consist, after all,
of a combination of subordinate machines. Thus the modern
grain-harvesting machine embodies a machine for moving to the place of
attack, a machine for cutting the grain, a machine for supporting the
grain at the instant of cutting, a machine for receiving the cut
grain, a machine for conveying the cut grain to a bindery, a machine
for measuring the cut grain into gavels, a machine for compressing the
gavel, a machine for applying the band, a machine for tying the band,
a machine for discharging the bundle, a machine to receive the bundles
and carry them to a place of deposit, and a machine to deposit the
accumulated bundles. The machine would be useful with one or more of
these sub-machines omitted, and each machine may be capable of
performing its own individual results alone or in other associations.
Pioneership of invention might apply to the main machine, or to the
sub-machines, or even to the sub-organization within the sub-machines.

(To be continued.)

* * * * *

[Continued from SUPPLEMENT, No. 1172, page 18764.]

THE DEVELOPMENT OF THE CENTRAL STATION.

By SAMUEL INSULL.[1]

[Footnote 1: Before the Electrical Engineering Department of
Purdue University, Lafayette, Ind., May 17, 1898.]

The success of the low-tension system was follo