Page:Transactions of the Provincial Medical and Surgical Association, volume 4.djvu/249

Rh celebrated and important experiment of Torricelli, the attention of some of the philosophers has been drawn, in succession, to this interesting problem; and the difficulty of estimating the quantity and effects of aqueous vapour, has hitherto been one of the chief obstacles to the attainment of accuracy. Daniell's hygrometer is, perhaps, better calculated than any other instrument, to remove this obstacle. This hygrometer was used in the measurement of the height of the Worcestershire Beacon, which has been deduced according to the formulae of Maskelyne, Hutton, and Daniell, from the following preliminary observations made by myself.