BTN Let the electricity flow

3 facts I have are that 1.Stephen Gray divided the world into two different kinds of substances conductors and insulators. 2.300 years ago Stephen Gray created a machine that could generate static electricity. 3.Glass, ceramic objects and silk are just some of the materials that insulate electricity.

2 understandings that I have now are that 1.Insulators hold the electric charge and 2.conductors let the electricity move freely.

A question I have is that why did Gray use an orphan to lie across the swings and not a random person?