At Tibur, in Tivoli, near Rome, in the gardens of Hippolitus d'Este, Cardinal of Ferrara, there are the representations of sundry birds sitting on the tops of trees, which, by hydraulic art, and secret conveyances of water through the trunks and branches of the trees, are made to sing and clap their wings; but at the sudden appearance of an owl out of a bush of the same artifice, they immediately become all mute and silent. It was the work of Claudius Gallus, as Possivenus informs us.