As the bottom one releases its water so the top one becomes heavier and begins to travel. It drops 500 feet down on a steep 800 foot track and pulls its partner up. The whole thing recycles water and uses no oil, fuel or electricity. It is in Devon and has been in operation since 1890. 40 passengers per carriage and no harm to the environment. It's £1.50 each way and a right old caper. We had fish and chips on the beach at the bottom and then explored the shore. Perfect English holiday.