244 cook's first voyage I769. 



the limits of the trade-wind, than upon any other 

 part of them. 



The tides about these islands are perhaps as in- 

 considerable as in any part of the world. A south 

 or S. by W. moon, makes high water in the bay of 

 Matavai at Otaheite ; but the water very seldom rises 

 perpendicularly above ten or twelve inches. 



The variation of the compass I found to be 4° 46' 

 easterly, this being the result of a great number of 

 trials made with four of Dr. Knight's needles, adapted 

 to azimuth compasses. These compasses I thought 

 the best that could be procured, yet when applied to 

 the meridian line, I found them to dilier, not only 

 one from another, sometimes a degree and an half, 

 but the same needle, half a degree from itself in dif- 

 ferent trials made on the same day ; and I do not re- 

 member that I have ever found two needles which 

 exactly agreed at the same time and place, though I 

 have often found the same needle agree with itself^ 

 in several trials made one after the other. This im- 

 perfection of the needle, however, is of no conse- 

 quence to navigation, as the variation can always be 

 found to a degree of accuracy, more than sufficient 

 for all nautical purposes. 



