Thanks for all the reply. Roger it is nice to see you posting here. I got your book and find it a great source of inspiration.
Today I look through the book by Mark Vieira on Hurrell's Hollywood Portraits....I found the answers!!! Hurrell liked to use lower wattage fresnels 500W or even 200W becuase they produce much less heat and blown out highlights. There was one exception when he placed a 1kw fresnel two feet away from Bette Davies in one photo. I think this is only possible becuase she looked down and maybe posed for a very short time. I would imagine she could get 2nd degree burn on her face if this lasted more than 10 minutes. I had black foams cookies/cutters placed 1 meter in front of the 1Kw Arri and it started to melt within minutes! I made the mistake of assumming a 1kW spot was not too much for portrait photography. Now I use an Elinchrom and a Bowen fresnels as keys instead of the Arri.
From the photos of Hurell's lighting settings, those boom lights seem to be very light weight maybe fresnels less than 6" in daimeter.
The fresnels used in the old days are not quite the same as the modern ones. Modern fresnels have smaller bulbs/filaments and more compact lens. I used to own a vintage 500w fresnel, its bulb and filaments are hugh. In order to accomodate the large bulb, the lens must be larger. Therefore, the fresnels seen in archive photos look quite large but they might not be installed with poweful bulbs.
Also, I believe soft lights (a rectangular white scoop reflector with linear tungsten bulb plus silk diffusion scrim on the front ) or sky pan (like the modern beauty dish) were often used as key in movies/still in 1930-40s to light female stars as characterised by a large catch light in their eyes. It would be less torture to look directly to the lights.