The air pump was one of the most important pieces of scientific equipment in the 17th century. Perfected by Robert Boyle and Robert Hooke, it allowed experimenters to create a partial vacuum in the glass bell at the top of the device by pumping air out using the handle. (Difficulties in getting the seals to work properly meant the mechanism was never absolutely air-tight.) Apart from proving that a vacuum was possible, the air pump gave rise to a huge number of experiments. One of the most famous (and popular with the Fellows) was putting a bird or small animal into the glass bell and watching what happened when the air was pumped out. Hauksbee, who designed this model, made scientific instruments and was elected a Fellow for his skill in conducting experiments with his own apparatus.