How did the invisible man first become visible?

The invisible man was a scientist, named Griffin. He swallowed certain rare drugs which made him invisible. It was mid-winter when he did the experiment so it was impossible to do without clothes. He slipped into a London store for shelter. When the store closed, he opened some of the boxes and unwrapped them. He adorned himself with shoes, an overcoat and a wide brimmed hat and became a fully dressed and visible person.