bristol fighter

Hello
This is my first post on this forum!
I do guided tours at IWM Duxford (on the subject of the Battle of Britain and the air defence of Britain 1914 – 1945) and one of the most frequent questions is:
What are those propellors on the wing for? (WW1 Bristol Fighter)
I think one is a dynamo but haven’t got a clue about the other one.
I know someone will be able to tell me!
Many thanks