NavList:

David wrote

I'm coming round to the idea that Hughes were probably toying around with the PZX solver concept so they didn't miss the boat if the idea suddenly became popular with the military, big companies, and others with purchasing power.

That idea had occurred to me. It was near the end of the hand-computed table era but before the digital era. An analogue device was the logical next step. If you look at Bowditch or the Rittenhouse article you will note that there were a large number of analogue methods in use or proposed.

Rittenhouse quotes Willis as saying (when talking about his navigating machine)

"Does for the navigtor what the adding machine does for the accountant."

As an aside the marine version of Willis' machine was estimated to cost $US500. Between 1936 and 2020 pices in NZ have increased approximately 57 times. I know that the US figures will be different but as a starting point the Willis Navigating Machine would have cost approximately $US28,000 in 2020 money. What a difference digital technology and smart phones have made.