King George's Sound.'] 
TERRA AUSTRALIA 
71 
This is what I allowed in tracing a base line upon the beach between 18 °2- 
Januar 
the two harbours ; and the back bearings from different stations did 
not vary more than a degree from it, except at the west end of 
Michaelmas Island, where the variation, in one spot, was greater by 3°. 
The above different variations show that the needle was 
affected by the rocks ; and there will be frequent occasion, in the 
course of the voyage, to point out similar anomalies in the observa- 
tions on land ; for they were found to take place upon almost all 
those parts of Terra Australis, where the basis stone is of granite, as 
here ; and also in those where green-stone, porphyry, basaltes, or 
iron-stone prevail ; whereas in the lime, or grit-stone countries, the 
needle did not appear to suffer any derangement. In the Appendix 
No. II. to the second volume, where the changes on ship board, which 
arose from altering the direction of the head, are explained, this sub- 
ject of the differences on shore is mentioned ; for they also were not 
without a certain degree of regularity. 
No set of Tide was perceived on board, either whilst the ship 
was in the Sound, or in Princess-Royal Harbour; nevertheless it was 
sometimes found to run with considerable strength in the narrow 
entrances of both harbours. According to lieutenant Flinders' ob- 
servations on shore,, during sixteen days, there was only one high 
water in twenty-four hours ; which always took place between six 
and twelve at night : for after, by gradually becoming later, it had 
been high water at twelve, the next night it took place soon after 
six o'clock ; and then happened later by three quarters of an hour 
each night, as before. The greatest rise observed was three feet two 
inches, and the least two feet eight inches. The accumulation was 
made in this manner : After low water, it rose for several hours ; 
then ceased, and became stationary, or perhaps fell back a little. In a 
few hours, it began to rise again ; and in about twelve from the first 
commencement, was high water. It was observed by captain Cook 
upon the east coast of this country,* and since by many others, 
* See Hawkesworth's Voyages, Vol. III. p. 224. 
