Sir H. Davy and his colleagues at the Board of Longitude have entire confidence in the scientific persons whom Sir T. Brisbane has on the spot, particularly Mr. Rumker, and gives the follows letter:—

MY LORD—The Right Honorable His Majesty's Secretary of State for the Home Department having done me the honor to inform me that your Lordship was favourably disposed to an undertaking which the Council of the Royal Society consider as important in the interests of Science, viz., the measurement of an arc of the Meridian in New South Wales, I take the liberty, at their request, of transmitting this to your Lordship. Several arcs have been measured in the Northern Hemisphere, but only one, and that at a time when instruments were very imperfect, in the Southern. The present moment appears peculiarly favorable for such a work to the Council, as there are persons at Parramatta who are able astronomers, and who are in possession of the necessary instruments, with the exception of a Zenith Sector. The measurement of an arc in New South Wales would not only be of importance to Astronomy in affording data for determining correctly the figure of the earth—a matter of great interest to navigation—but would likewise be useful in laying the foundation for a correct survey of our Colonies in that great and unexplored country. Your Lordshop's liberal and enlightened mind will, I am sure, require no apology for this communication which, as President of the Royal Society, the interests of Science call upon me to make.

I have the honor to be, my Lord,
With the greatest respect,
Your Lordship's obedient humble servant,
HUMPHREY DAVY
President of the Royal Society.

The unfortunate interruption of Sir Thomas' design by the action of Mr. Rumker made this impossible, and when Rumker was appointed by the Government it was evidently understood, although not conveyed to him in his letter of appointment, that he should measure the arc of the meridian. Mr. W. D. Campbell in searching for other things connected with the surveys of the Colony, found amongst the MS. Correspondence, Surveyor-General to Colonial Secretary, (Vol. I., p. 507, 8th January, 1828)—"The requisition for the rods and cylinders for the Trigonometrical Survey was made by Mr. Rumker, the survey being in conjunction with the measurement of an arc of the meridian, which Mr. Rumker had undertaken to execute."

And the pendulum apparatus which was used by Rumker at Parramatta, and with which he made the length of the Seconds Pendulum there to be 39.0891435 inches, was evidently brought out to be used in connection with the measurement of an arc of the meridian.

With the instruments that came from the Parramatta Observatory to Sydney, when it was dismantled, was a zenith sector which appears never to have been used, but is a large one and evidently intended for accurate work. A transit circle also came in the same way, and it would appear that this instrument was very little, if at all, used, and there was no room for it in the original building hence it was set up on the outside of it. It was a good instrument, and, with some repairs, did duty in Sydney Observatory from 1859 to 1876, and it is still there, but not in use.

The transit circle in its day, 1830, was justly considered a first-class instrument, and must have been intended for accurate determination of star positions for the measurement of the arc of the meridian.

Bureau of Meteorology