Richard Harrison wrote:

Cecil Moore, W5DXP is alleged to have written:

Jim Kelley actually claims to have written it.

"Nor will we find a negative scalar quantity accompanied by the claim
that the negative sign indicates a change in direction as you have
done."

Have not read Hscht, but I`ve read Terman and realize that a
transmission line can guide a wave only forward and backward. Sometimes
backward is considered the negative direction.

Yes, for vector quantities expressed as a function of position or time.

Terman gives an example on page 90 of his 1955 edition:
"When the load end of the line is shorted, that is Eload =0 , reference
to Eq. (4-14) shows the reflection coefficient has the value -1.0 on an
angle of 0-deg.= 1.0 on an angle of 180-deg. As in the open-circuited
case, the reflected wave has an amplitude equal to the amplitude of the
incident wave. However, the refleection now takes place with a reversal
in phase of the voltage and without change in phase of the current."

From Webster's Collegiate:
Scalar - a quantity such as mass or time that has a magnitude
describable by a real number and no direction

Power as a scalar quantity does not have direction, and so one could not
for example subtract power 'moving' in one direction from power 'moving'
in the other direction by arbitrarily multiplying one of the magnitudes
by negative one.

73, ac6xg