[HiTech RedNeck]

The first thing to break down would not be the silk, but the air. Franklin was still pretty lucky. The key was close enough to draw an arc to his knuckles when he reached out.

[hellbender]

The first thing to break down would not be the silk, but the airI'm not so sure about that. What is the conductivity of air vs. silk? Also, in conditions which are getting favorable for lightning, the charge often appears already around things which may be not very conductive, but reach higher than other objects (St. Elmo's fire). I think Franklin's idea that silk was safe was based on experiments in parlors. He really didn't know that he was dealing with millions of volts in a thunderstorm.