Narrative of the surveying voyages of his majesty's ships Adventure and Beagle (vol.2- Appendix): between the years 1826 and 1836 : describing their examination of the southern shores of South America, and the Beagles's circumnavigation of the globe

appi-:ndix. 281 from near Pernambuco to the vicinity of the river Plata ; and lastly^ the ahnost uniformity of the time of high \A'ater along that extent of -the coast of Africa which reaches from near the Cape of Good Hope to the neighbourhood of the Congo. Against the supposition that a tide-wave travels along the west coast of America, from north to south, are the facts — that the flood- tide impinges upon Chiloe and the adjacent outer coast, from the southward of west ; that it is high water at Cape Pillar and at Chiloe, inclucUng the intermediate coast, almost at one time ; * that from Valdivia to the Bay of Mexillones (differing eighteen degrees in lati- tude), there is not an hour's difference in the time of high- water that from Arica to Payta the times vary gradually as the coast trends westward ; that from Panama to California, the times also change gradually as the coast trends westward ; and that from forty to sixty north, high water takes place at one time. Having thus stated a few of the difficulties to be encountered by a theory which supposes such important tide -waves to move in the di- rection of a meridian, rather than in that of a parallel, I will venture to bring forward the results of much anxious meditation on the subject, trusting that they will be received by the reader — not as assertions — not as conclusions to which assent is asked without a reason for acquiescence being given — ^but as the veiy^ fallible opinion of one indi\'idual, who is anxious to contribute a mite, however small, towards the information of those for whom this work is more parti- cularly vmtten — namely, seafaring men ; and who, if his ideas are fallacious, will rejoice at their refutation by the voice of truth. Resting in confidence upon the Nevrtonian theory — which assigns as the primary causes of tides the attractions of the moon and sun I win make a few remarks, and then state some facts from which to reason. Some persons seem to view the tidal phenomena more in con- nection with what would have happened had the globe been covered with water, than with reference to what actually happens, now that the oceans are nearly separated by tracts of land. They appear to consider that the effects of the moon's attraction (leaving the sun's out of the question at present, as it is similar though smaller) are felt only in vertical hues ; and they do not allow for the lateral action of * Within about half an hour; an irregularity easily accounted for, and to which any one place is subject. bb