Thank you Ed, much appreciated and I'm grateful. I know what the jet stream is, in fact the phenomenon was identified by an English clergyman, William Clement Ley, in a series of articles during the 1870s (true, I promise you), but that's part of my research. My real interest is in the actual translation of Seilkopf's "Strahlströmung". Today that translates as "jet flow aka stream", but a 1939 handwritten translation in the (British) Meteorological Office archives uses the words "radiant flow", not once but several times. I cannot for the life of me understand where "radiant" comes from and my post was an attempt to find if "Strahlströmung" had a different meaning at that time.
I've no doubt that the Chicago meteorologists were aware of Seilkopf's work, and perhaps should have acknowledged that was the source of their term "jet stream".
I think the claim that American pilots flying over Japan 'discovered' the jet stream (
https://apps.dtic.mil/sti/tr/pdf/AD0036014.pdf from your suggestion) is rather stretching it, as there are several accounts of both USAAF and RAF crews encountering jet streams over the continent prior to those flights.
Brian