Linncean Suciety. 357 



power of inherent attraction of aggregation. The phaenomena of cry- 

 stallization and of cleavage prove that the molecules of crystals have 

 several axes of attraction, or lines along which they are most power- 

 fully attracted, and in the directions of which they cohere with dif- 

 ferent degrees of force. Guided by the indications of hemitrope forms, 

 and supposing the molecules to be spherical or spheroidal, it is in- 

 ferred that these axes are three in number, and at right angles to each 

 other, and that they are related in position to the geometrical axis of 

 the primitive form. In like manner, the phaenomena of double refrac- 

 tion are related to the same axis of the primitive form ; and may be 

 all rigorously calculated by a reference to three rectangular axes. 

 The author pursues the consequences of these principles in their ap- 

 plication to various kinds of crystals. It follows, from this theory, 

 that the forms of the ultimate molecules of crystals existing separately, 

 determines within certain limits the primitive form to which they 

 belong, while the doubly-refracting structure and the precise form of 

 the crystal are simultaneously produced by the action of the forces 

 of aggregation. These views receive a remarkable confirmation in 

 the doubly-refracting structure which the author discovered in cha- 

 basite j and they also enable us to understand the nature of that in- 

 fluence which heat produces on doubly-refracting crystals, as dis- 

 covered by Professor Mitscherlich. The optical phsenomena exhibited 

 by fluids under the influence of heat and pressure, and by crystals 

 exposed to compressing or dilating forces, are also in perfect confor- 

 mity with the above views, and would in themselves have been suf- 

 ficient to establish the principle that the forces of double refraction 

 are not resident in the molecules themselves, but are the immediate 

 result of those mechanical forces by which these molecules constitute 

 solid bodies. 



LINN^AN SOCIETY. 



April 6. — The President, Lord Stanley, in the chair. 



A furtlier description was read of the Anatomy of the Mammary 

 Organs of the Kangaroo. By J. Morgan, Esq. F.L.S. 



This paper is a sequel to one already printed in the Transactions of 

 the Society, and contains some important additional information, sub- 

 sequently derived from an examination of living and dead subjects.* 



April 20. — The President in the chair. 



A paper was read, — On Luminous Insects, by Mr. Richard Cham- 

 bers, F.L.S. 



The paper maintains, on the testimony of various authorities, (some 

 selected from books, and some collected from original sources by the 

 author,) that IgnesfatuinK luminous insects ; and supports this opi- 

 nion by tlie facts often observed, that they alight on various objects, 

 and bound over ollicrs. 



There was exhibited the cuticle of the hand and foot of a person 

 from vvliom its exfoliation had occurred five several times, after severe 

 iittaiks of fever. 



• An abstract of Mr. Morgan's former paper will be f'ouud in Phil. Mag. 

 and Annal?, vol. iii. pp. 375 & 4 10. 



GEO- 



