Page:A Voyage to Terra Australis Volume 2.djvu/60

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Captain Cook observed, when taking bearings upon the top of Pier Head, "that the needle differed very considerably in its position, even to thirty degrees, in some places more, in others less; and once he found it differ from itself no less than two points in the distance of fourteen feet." (Hawkesworth, III, 126); from whence he concluded there was iron ore in the hills. I determined, in consequence, to make more particular observations, both with the theodolite and dipping needle; and shall briefly state the results obtained on this, and on the following day.

Azimuths were taken, and the bearing of Mount Westall, distant thirty-four miles, was set at S. 63° 28′ E. (true), whilst the theodolite remained in the same place; and from a comparison between this bearing and those of the same object at different parts of the head, the variations were deduced. The dip was observed with both ends of the needle, and the face of the instrument changed each time.

There are here no differences equal to those found by captain Cook; but it is to be observed, that he used a ship's azimuth compass, probably not raised further from the ground than to be placed on a stone,