The first section. Shewing the occasion of making this new Essay - Instrument, together with the hydrostatical principle' tis founded on

Abstract

To give you now a more explicite and particular Account, than I had then time to do, of the Instrument which you saw tried at the Royal Society, I shall inform you, on what Grounds I devis’d it, and then annex some Observations about the Fabrick and the Uses of it.