21 March

According to arrangements made with Captain King and Mr. Dunlop, the
King’s astronomer at the Parramatta observatory, I halted the party this
day in order to make hourly observations of the barometer, thermometer,
the sky, etc. This plan had been strongly recommended by Sir John
Herschel; and for our present purposes it was most desirable in order
that we might ascertain how far the fluctuations of the atmosphere in two
places so distant as Parramatta and Byrne’s creek corresponded in these
simultaneous observations. During our last journey some discrepancies in
the heights determined by the barometer on the Darling led to a suspicion
that the fluctuations at such great distances, in situations so
dissimilar, might vary considerably; and this was now to be ascertained.