^80 



APPENDIX. 



Some of the facts which seem to stand most in opposition to the 

 theory that deduces tides in the northern Atlantic from the move- 

 ment of a tide-wave originated in the great southern ocean are : 

 — the comparative narrowness of the space between Africa and Ame- 

 rica ; with the certainty that the sea is neither uniformly nor exces- 

 sively deep in that space,* and the trifling rise of tide ; not only 

 upon either nearest shore (where it does not exceed four or five feet 

 at the utmost), but at Ascension Island, where the highest rise is not 

 two feet.f Secondly, the absence of any regular tide about the wide 

 estuary of the river Plata, the situation and shape of which seems so 

 well disposed for receiving an immense tide 4 Thirdly, the flood- 

 tide moving towards the west and south along the coast of Brazil, 



rent from that which we have taken. The course of these lines in the 

 Pacific appears to be altogether problematical ; and though those which 

 are drawn in the neighbourhood of the west coast of America connect 

 most of the best observations, they can hardly be considered as more than 

 conjecture : in the middle of the Pacific I have not even ventured to con- 

 jecture. Tt only remains to add, that I shall be most glad to profit by 

 every opportunity of improving this map, and will endeavour to em- 

 ploy for this purpose any information with which I may be supplied."— 

 pp. 234-5. 



* Besides the ' Roccas', Fernando de Noronha, and St. Paul rocks, 

 various accounts have been received, from time to time, of shoals near the 

 equator, between the meridians of fifteen and twenty-four degrees west. 

 There can be no doubt, from the descriptions, that many alarms have been 

 caused in that neighbourhood by earthquakes; which are, to my appre- 

 hension, indications of no very great depth of water. In 1761, a small 

 sandy island was said to have been seen by Captain Bouvet, of Le Vail- 

 lant. This, if seen, has probably sunk down since. Krusenstern saw a 

 volcanic eruption thereabouts in 1806. In 1816, Captain Proudfoot, in 

 the ship Triton, from Calcutta to Gibraltar, passed over a bank, in lati- 

 tude 0° 32' S. and longitude 17° 46' W. It appeared to extend in an east 

 and west direction three miles, and in a north and south direction one 

 mile. They sounded in twenty-three fathoms, brown sand ; but saw no 

 appearance of breakers. 



t At St. Helena it is not three feet : while at Tristan d'Acunha there 

 is a rise of eight or nine feet under ordinary circumstances. 



I I have passed months in that river without being able to detect any 

 periodical rise of water, which I could attribute to tide ; though it is said, 

 that when the weather is very settled, some indications of a tide may be 

 perceived. 



