[Antipodal]

There was an interesting article in a "Radio Craft" about 1936 or 1937 when the metal tubes first appeared.The particular aspect the article concerned itself with was the temperature of the  glass versus metal tubes - which ran hotter,which dissipated the heat more effectively/efficiently but also other aspects such as inter -electrode capacitance differences if I remember correctly.I got the feeling the article was written by someone independent so it was not an advertorial.