274 Proceedings of the British Associalion 



transferred by hand to the gelatine paper the silver plates had lo be 

 cleaned off, olherwise it is obvious ihey would soon multiply lo a num- 

 ber too expensive and cumbrous lo be used. Now, he had strong 

 doubts that any person could transfer by hand all the minute fluclua- 

 lions of the instrument; he did not now speak of the great magnetic 

 storms, the indications of which were constant and universal, but he 

 alluded to those sudden, slight, but now important agitations which the 

 instrument seemed to undergo after working on each side of its mean 

 position with great steadiness. And yet, from the recent discovery of 

 Prof, Faraday as to the varying relations of oxygen to magnetism by 

 alterations of the temperature, it became highly probable that these 

 same slight waverings of the magnetometer would be found to have an 

 interest attached to them hitherto altogether unsuspected. 



4. On our Ignorance of the general course of the Tides ; by Dr. 



■i 



Whewell. 



Wh 



an essay towards a first approximation to a map of co-tidal lines; in 

 which he attempted, from the data then accessible, to draw lines ex- 

 pressing the course of the tide wave all over the ocean. So far as the 

 coasts are concerned, this mode of expressing the course of tides is 

 still held to be the best; but our materials, which were scanty at the 

 former period, are very incomplete even yet, with the exception of the 

 coasts of Europe and the east coast of North America, the east coast 

 of Australia, and the east coast of New Zealand. In order to trace 

 the course of the tides on any coast, we ought to know the points of 

 divergence and of convergence of the tidal wave. We do not know 

 these points on the west coast of Africa, or on the east coast of South 

 America; and consequently we do not know the course of the tides of 

 the Atlantic, nor do we know the relation of the tides of the Atlantic 

 islands, (the Ferroes, Azores, Bermudas, Cape Verde Islands, &Cm) fo 

 the tides of the coasts. It was urged that the course of the tides in 

 this and other oceans could not come to be known except by an expe- 

 dition, consisting of one or two smalt vessels, which should have for its 

 primary and governing object the obtaining a connected knowledge of 

 the tides of the coasts of the Atlantic, in the first place, and of those 

 of other oceans afterwards. 



The Astronomer Royal said that the inquiries to which Dr. Whewell 

 had now directed their attention had an object definite, intelligible, and 

 most important, whether we considered it practically in its bearing on 

 commerce and our navy, or as an object of pure science, in furnishing 

 the data requisite for advancing our knowledge on this interesting yet 

 intricate branch. In such a case he found itto be always a most im- 

 portant matter to make a beginning, however humble, and from his 

 own experience he could assure Dr. Whewell that he felt convinced if 

 a proper application were made to the government to observe the tides 

 carefully in the manner pointed out by Dr. Whewell in some limited 

 locality, — say in the Atlantic Ocean, — such an application would meet 

 with the attention which it so well deserved, and which he at all times 

 found the government cheerfully to bestow on such matters. He had 

 not the least objection, should such an application be deemed proper 



