306 Royal Society : — 



gradational, can only be considered as distinguishing individuals. 

 It thus follows that a very wide range of variation exists in this 

 type ; so that numerous forms which would be unhesitatingly 

 accounted specifically different, if only the most divergent examples 

 were brought into comparison, are found, by the discovery of those 

 intermediate links which a large collection can alone supply, to be- 

 long to one and the same specific type. 



After noticing some curious monstrosities, resulting from an un- 

 usual outgrowth of the central nucleus, the author proceeds to in- 

 quire Into the essential character of the Orbitolite, and its relations 

 to other types of structure. He places it among the very lowest 

 forms of Foraminifera ; and considers that it approximates closely 

 to sponges, some of which have skeletons not very unlike the cal- 

 careous net- work which intervenes between its fleshy segments. Of 

 the species which the genus has been reputed to include, he states 

 that a large proportion really belong to the genus Orbitoides, whilst 

 others are but varieties of the ordinary type. This last is the light 

 in which he would regard the Orbitolites complanata of the Paris 

 basin ; which differs from the fully-developed Orbitolite of the 

 Australian coast in some very peculiar features (marking a less com- 

 plete evolution), which are occasionally met with among recent 

 forms, and which are sometimes distinctly transitional towards the 

 perfect type. 



The author concludes by calling attention to some general prin- 

 ciples, which arise out of the present inquiry, but which are appli- 

 cable to all departments of Natural History, regarding the kind and 

 extent of comparison on which alone specific distinctions can be 

 securely based. 



June 21. — The Lord Wrottesley, President, in the Chair. 



The following communications were read : — 



"On the Magnetism of Iron Ships, and its accordance with 

 Theory, as determined externally, in recent Experiments." By the 

 Rev. W. Scoresby, D.D., F.R.S. 



The magnetic condition of iron ships is a subject of so much im- 

 portance, practically and scientifically, that I have been induced to 

 submit to the Society a few characteristic facts (hastily indeed 

 brought together) derived from recent experiments. 



In a work in the Society's library, entitled ' Magnetical Investi- 

 gations,' it was shown, by deductions from an elaborate series of 

 experiments on plates and bars of malleable iron, that the magnetic 

 condition of iron ships should, theoretically, be conformable to the 

 direction of terrestrial induction whilst on the stocks ; and the re- 

 tentive quality, which is so highly developed by virtue of the ham- 

 mering and other mechanical action during the building, should be 

 so far fixed in the same direction, as to remain after the ships might 

 be launched, until disturbed by fresh mechanical action in new posi- 

 tions of their head or keel. In this view, taking, for instance, the 

 condition of the middle, or the main-breadth section of a ship on 

 the stocks, the magnetic polar axis should assume the direction of 



