While pondering the fact that 57 seconds is a long time to go 850 ft (best
and third flight on Dec 17th) it occured to me that it was very windy at the
time.
I believe the bros. reported in the telegram home to dad that it was 21 mph.

850 ft in 57 seconds is 894 ft per minute or about 10 mph. Add that to the
21 and you get an average airspeed of 31 mph.

31 mph for 57 seconds means they actually travelled through the air for just
about half a mile!

I wish I'd though of that before.

Using this rough logic, even the very first hop was equivalent to more than
350 ft.