284 



APPENDIX. 



In the greatest expanse of ocean, that which meets with only par- 

 tial interruption to free tidal movements — the zone, if it maj"- be so 

 called, near fifty-five degrees of south latitude — there Is high water at 

 opposite sides, and low water at opposite sides of the globe nearl}'^ 

 at the same time. 



At the eastern part of the Falkland Islands, exposed to the tide of 

 this zone, it is high water, or full sea, at about nine o'clock on the 

 day of new, or full moon, by Greenwich time ;* and on the southern 

 shore of Van Diemen's Land it is high-water at about ten. This is 

 not a point exactly opposite, it is true, but it is the nearest so at 

 which we have yet observed. 



At each of tliese places the tide rises six hours and falls six hours, 

 alternately ; therefore when it is low water at one, it is also low water 

 at the other. There is no intermediate place in this zone, rather 

 distant from these points, at which I know of a tide observation 

 deserving confidence ; but those above-mentioned are certain, and 

 corroborate the Newtonian theory in a satisfactory manner. 



This is, however, the only zone of ocean, which is at all able to 

 follow the law which would govern its undulations if the globe were 

 covered with water. In other zones (taking about ten degrees 

 in latitude as a zone) it is high water, generally speaking, at one 

 side of an ocean near the time that it is low on the other. 



In oceans about ninety degrees wide, this happens very nearly ; 

 but as the width diminishes, so do the times of high water at each 

 side approach ; and as the viidth increases beyond ninetj' degrees, as 

 in the case of zones of the Pacific, the times of high water still 

 approach (in consequence of the tendency to high M'ater at opposite 

 points), and farther confirm the Newtonian theory. 



For examples (on the day of full moon) : — In the Pacific, at Port 

 Henry, in 50° S. it is high water at 5h. at M'hich time it is near low 

 water at Auckland Island, where the time of high tide is 12h. 30m. 

 In this case, the interval between one high water, and the other on 

 the opposite side of the ocean, is 7h. 30m. or 4.30 ; and the ^vidth of 

 that ocean is nearly eight hours (measured in time.) 



At Valdivia, in lat. 4C° S. it is high water at 3h. 30m. and at New 

 Zealand, on that parallel, at 9h. 50m. The space of ocean between 

 is seven hours nearly : the diflTerences are 6.20 and 5.40. 



* Towhicli all tlio tinips are iiere reduced for easy comparison. 



