the
controlling hand can have no proper or customary rest, the motion must
be from the shoulder and with the whole arm. The writing will
therefore be upon an enlarged scale, loose, sprawling, and can have
little, if any, characteristic resemblance to the natural and habitual
style of the controlling writer, and of course none of the person's
whose hand is passive.

In appearance it changes abruptly from very high or very wide to very
low or narrow letters. This is to be explained by the non-agreement in
phase of the impulses due to each of the two writers. If both are
endeavoring at the same moment to write a given stroke the length of
that stroke will be measured by the sum of the impulses given by the
two writers. If they act in opposition to one another, one seeking to
make a down stroke while the other is trying to make an up stroke, the
result will be a line equal to the difference between the stronger and
the weaker force.

As these coincidences and oppositions occur at irregular but not
infrequent intervals, like the interference and amplification phases
of light and sound waves, the result traced on the paper might be
expected in advance to be--and in fact is--a distorted writing where
maxima and minima of effect are connected together by longer or
shorter lines of ordinary writing.

The only state of things which can justify the guiding of a hand
executing a legal instrument is the feebleness or illness of its
owner.

When such assistance is required it is usually given by passing the
arm around the body of the invalid and supporting the writing hand
while the necessary characters are being made.

Both participants in this action are looking at the writing, and both
are thinking of the next letter which must be written, and of the
motion of the pen necessary to produce it. Unless the executing hand
were absolutely lifeless or entirely devoid of power, it would be
impossible for it not to influence the guiding and presumably stronger
hand; for the least force exerted cannot fail to deflect a hand,
however strong, in an unnatural and cramped position. Nor can the hand
of the guider fail to add its contribution to the joint effort,
however much the brain which controls it may strive to render the hand
entirely passive. Both minds are busy with the same act, and
insensibly both hands will write the same letter with the results just
described.

Can the characteristics of each hand be separated from those of