12 REPORT — 1839. 



Beagle, just published, there is an article in the Appendix, containing 

 remarks on the tides. Captain Fitzroy observes, that facts had led him 

 to doubt several of the assertions made in Mr. Whewell's memoir, pub- 

 lished in the Philosophical Transactions, 1833, and entitled 'Essay 

 towards a First Approximation to a Map of Cotidal Lines.'* — (Appendix, 

 p. 279.) Prof. Whewell stated, that he conceived that douhls, such as 

 Captain Fitzroy 's, are reasonable, till the assertions are fully substan- 

 tiated by facts. Captain Fitzroy has further offered an hypothesis of 

 the nature of the tidal motion of the waters of wide oceans, diiferent 

 from the hypothesis of a progressive wave, which is the basis of Prof. 

 "Whewell's researches. Captain Fitzroy conceives that in the Atlantic 

 and the Pacific the waters oscillate laterally between the eastern and 

 western shores of these oceans, and thus produce the tides. This sup- 

 position would explain such facts as this, that the tide takes place 

 along the whole west coast of South America at the same time ; and 

 the supposition might be so modified as to account for the absence of 

 tides in the central part of the ocean. Prof. Whewell stated, that he 

 was not at all disposed to deny that such a mode of oscillation of the 

 waters of the ocean is possible. Whether such a motion be consistent 

 with the forces exerted by the sun and moon, is a problem of hydrody- 

 namics hitherto unsolved, and probably very difficult. No demonstra- 

 tive reason, however, has yet been published, to show, that such a 

 motion of the ocean waters may not approach more nearly to their 

 actual motion, than the equilibrium theory, as usually applied, does. 

 When the actual phaanomena of the tides of the Atlantic and Pacific 

 have been fully explored, if it appear that they are of the kind supposed 

 by Captain Fitzroy, it will be very necessary to call upon mathemati- 

 cians to attempt the solution of the hydrodynamical problem, either in 

 a rigorous or in an approximate shape. 



On the best Positions of three Magnets, in reference to their mutual action. 

 By the Rev. Professor Lloyd, F.R.S. 



It is a problem of much importance, in connexion with the arrange- 

 ment of a magnetical observatory, to determine the relative position of 

 the magnets in such a manner, that their mutual action may be either 

 absolutely null, or at least readily calculable. Such was stated by 

 the author to be the object of the present investigation. In the 

 case of two horizontal magnets, one of which (intended for obser- 

 vations of declination) is in the magnetic meridian, and the other (used 



* Among the points which I could not establish in my own mind, by appeal to fac^s, 

 were: — " The tides of the Atlantic are, at least in their main features, of a derivative 

 kind, and are propagated from south to north ;" "that the tide-wave travels from the 

 Cape of Good Hope to the bottom of the Gulf of Guinea, in something less than four 

 hours; that the tide-wave travels along this coast (American) from north to south, em- 

 ploying about twelve hours in its motion, from Acapulco to the Strait of Magalhaens;" 

 " from the comparative narrowness of the passage, to the north (of Australia), it is al- 

 most certain that these tides must come from the southern end of the continent." "The 

 derivative tide, which enters great oceans (North and South Pacific) from the south- 

 east, is diffused over so wide a space that its amount is greatly reduced." 



