'Guinea and feather' experimental apparatus, 1761.
© Science Museum / Science & Society Picture Library
This apparatus consists of a glas barrel with a bras release device. In a replica of an 18th century experiment, all the air is pumped out of the glas tube so that there is no resistance to a falling object. A feather and a golden guinea are then released one after the other. They are found to accelerate at precisely the same rate. The apparatus was made by George Adams of Fleet Street, London, instrument maker to the king.