555 



there are as many of one kind as the other. After they have 

 acquired a certain breadth about one-twelfth, or the one-eighth of 

 an inch, the central part of the cyst appears to be drawn inwards, 

 forming a hollow ; at the bottom of which, the granular material 

 is deposited from which the suckers, booklets, and calcareous 

 granules are formed, as above described. 



December 20, 1855. 

 The LORD WROTTESLEY, President, in the Chair. 



The President stated that Robert William Sievier, Esq., who by 

 reason of non-payment of his annual contribution ceased to be a 

 Fellow of the Society at the late Anniversary, had applied for re- 

 admission ; and an extract of his letter to the Council was read, 

 explaining the circumstances under which, during his absence on 

 the continent, the omission of payment had taken place. Notice 

 was accordingly given, that the question of Mr. Sievier's re- 

 admission would be put to the ballot at next meeting. 



The following communication was read : 



" Further Researches on the Polarity of the Diamagnetic 

 Force/' By JOHN TYNDALL, Ph.D., F.R.S. Received 

 November 27, 1855. 



The author commences by referring to the results recorded in 

 the Bakerian Lecture for 1855. The fact of diamagnetic polarity- 

 was there established, by permitting fixed magnets to act upon a 

 moveable bar of bismuth, encircled by an electric current ; and, 

 from the deflections of the bar, the character of the force acting 

 upon it was inferred. The experiments recorded in the present 

 paper may be regarded as complementary to the above. Here dia- 

 magnetic bars, suitably excited, are permitted to act upon an 

 astatic system of steel magnets, and from the deflections of the 

 system, the polarity of the bodies acting upon it is inferred. An 

 experiment of the nature here indicated was made, three years ago, 



VOL. VII. 3 C 



