I am curious, did they mention anything about the "shadow" cast from
a piece of leader? ....

It's been a long time, Warren, and I seem to be getting more senile
every day, but I don't think so.

If so, do you know the name of the book or article so that I can read it?

I believe Harvey's discussion is in his book _Techniques of Trout
Fishing and Fly Tying_.

Marinaro's, IIRC, is in either _Modern Dry Fy Code_ or _In the Ring of
the Rise_. More likely in the latter, I think.

I'm going out of town for the weekend. When I get back, if no one
else has provided the answer, I'll try to find the references.

vince