here), we find a passage that we have quoted and discussed previously. See here.
The second paragraph in this passage reads:
"The ship drove on as she had done for a pair of weeks, pulsing in and out of four-space at thousands of times per second..." (p. 160)
The sf device of hyperspace is often associated with the fourth dimension which would give us "four-space." However, as this passage makes clear, the version of "hyperspace" used in Poul Anderson's Technic History involves not a warp or detour through the fourth dimension but multiple instantaneous quantum jumps within three dimensional space. Thus, the phrase "four-space" seems to be a hangover from more conventional accounts? Unless the theory is that a quantum jump does take an object through the fourth dimension?
I am posting over breakfast and must shortly travel by car, not hyperspace, to a nearby town so there will be blog silence from this part of Lancaster for a while.