188 



that the arrangement of the magnetism dnrino- the time that the elec- 

 tric current traversed the helix, appeared not to be the same as after 

 the cessation of that current : in the one case similar, and in the other 

 dissimilar, poles being opposed to each other at the opposite extre- 

 mities of the two semi-circles. 



Whether the magnetism was originally developed in the soft iron 

 by means of an electric current passing round it, or by passing over 

 its surface the poles of an electro-magnet, or those of a common mag- 

 net of hard steel, it appeared to possess the same power of retaining 

 a large portion of the magnetism thus developed. The retention of 

 the magnetism does not appear to depend upon the relative positions 

 of the ends of the horse-shoe and the keeper remaining undisturbed, 

 but on their contact remaining unbroken : for one keeper was substi- 

 tuted for another without diminution of this power : care being taken 

 that the second should be in good contact with both ends of the 

 horse-shoe before the complete removal of the first. 



This power of soft iron to retain the magnetism developed in it was 

 also shown by the action of the ends of the horse-shoe magnets upon 

 a magnetized needle ; by the attraction of iron filings; and by the 

 evolution of the electric spark, by means of a suitable apparatus, on 

 the sudden rupture of the contact between the keeper and the horse- 

 shoe, when several days had intervened since the removal of the bat- 

 tery by which the magnetism had been originally developed. 



The author's views on entering upon these experiments were, that 

 the soft iron, with its keeper, resembled a closed voltaic circuit ; but 

 they have convinced him that the phenomenon of the permanency of 

 the magnetism resolves itself into a case of complex induction, be- 

 tween the soft iron horse-shoe and the keeper. 



May 2, 1833. 



HIS ROYAL HIGHNESS THE DUKE OF SUSSEX, K.G., 

 President, in the Chair. 



The Right Honourable the Earl of Darnley was elected a Fellow 

 of the Society. 



A paper was read, entitled, <( Essay towards a first approximation 

 to a Map of Cotidal Lines." By the Rev. V»"illiam Whewell, M.A. 

 F.R.S. Fellow of Trinity College Cambridge. 



The general explanation of the phenomena of the tides originally 

 given by Xewton, although assented to by all subsequent philoso- 

 phers, has never been pursued in all the details of which its results 

 are susceptible, so as to show its bearing on the more special and 

 local phenomena, to connect the actual tides of all the different parts 

 of the world, and to account for their varieties and seeming anoma- 

 lies. The first scientific attempt that was made to compare the de- 

 veloped theory with any extensive range of observations, was that of 

 Daniel Bernouilli in 1740: the subject has since been pursued by 

 Laplace and Bouvard, and still more recently by Mr. Lubbock. But 



