About ten days ago I posted a message saying George Harvey and Vince
Marinaro had demonstrated that the purpose of fine tippets is to
combat drag, not to be invisible to trout. I've had time to do some
checking.

Here is a quotation from Harvey's _Techniques of Trout Fishing and
Fly Tying_, revised edition, pages 20-21:

"I made my way to the head of a flat pool I knew held a good
population of trout. I sat down upon the bank and started a chum line
of [Japanese] beetles. It wasn't long until I had about a dozen
trout taking every beetle that floated down. Now I took twenty-inch
pieces of hard nylon of all sizes I had with me and inserted the end
of the nylon into some of the beetles and sent them down the chum
line. Since there was no drag on the nylon, the browns picked off
most all of the beetles that were attached to the nylon.

"This was not my idea. I had read of a similar experiment
conducted by John Crowe and I wanted to check it for myself. Let me
tell you, I was really impressed. Most of what we read today and what
most fly fishermen believe is that the fine terminal part of the
leader is more invisible and that this is the reason for using fine
tippets. In fact many articles have been written that recommend that
the size of the terminal tippet should be determined by the size of
the fly one is using. This experiment blasts that theory because the
stream-bred browns did not refuse a live beetle on the free-floating
and drag-free pieces of nylon is sizes up to .015."

A shorter description of this experiment can be found in _George
Harvey: Memories, Patterns ands Tactics_, as told to Daniel L.
Shields, p. 71.

I was unable to find anything about this in Marinaro's _Modern Dry Fly
Code_. Perhaps it's in his _Ring of the Rise_, or perhaps my memory
was faulty and he did not do a similar experiment.

I'll check _Ring of the Rise_ when I can find time.

vince