Cecil, W5DXP wrote:
"Is the graph impedance looking into 1/2 of the dipole?"

I only quoted from the plot for tthe whole dipole in free-space.

The graph on page 345 has two traces:

Zo, or antenna average surge impedance, ZA, for a balanced, center-fed
dipole in free-space, which is found to be a function of the antenna
thickness=

ZA = 276 log 1/P

The other formula is also plotted. It is for a vertical rod against
ground. It has exactly 1/2 the resistance of the dipole.

For peripheries larger than 0.25 wavelength, Bailey notes that surge
impedance departs from the formula. For smaller peripheries, the plots
are almost straight lines on the scale used. Peripheries are plotted
with log spacings. Impedances are plotted with linear spacings.

Best regards, Richard Harrison, KB5WZI