[BUG] The Valley and The Wire placement

[Tevian Dray]

I normally have students do these activities a week apart, although this is
in part to the constraints of a large lecture with multiple recitations. 
I often don't actually talk about line integrals until after students have
done the Valley, talking students through the integrals during the activity.
During the week in between, I then talk about line integrals, the "use what
you know" strategy, and independence of path, although I save the Murder
Mystery Method for after the Wire.  Again, this timing is due in part to the
constraints imposed by the course structure, but it seems to work pretty well.

Tevian

PS: Today for the first time I used the Hill lab without first having reviewed
the gradient in class -- it's officially part of the previous course, although
students are often not very fluent with it.  Seemed to go OK.  I did hand
students the topo map (problem 1) due to time constraints (only 50 minutes)
and concern about the extra time needed to talk them through the use of the
gradient.