107 



heavier Iserine is left on the shore/ while the lighter parts of 

 the rock are washed away. 



Mr. Edward Hiqgin exhibited a fine specimen of the 

 Snake Nut (Ophiacarpa paradoxus, family of Sapondacese; 

 first discovered and described by the Chevalier Schomburgk, — 

 Annals of Natural History, 1840, vol. v., p. 202,) from the 

 Essiquibo river, in which the form of the head and the coils of 

 a serpent ready to spring, were singularly life-like. He also 

 exhibited a flint stone found at Grange, near Cartmel, with a 

 very perfect and beautiful impression of a Cidaris upon it. 



Dr. Inman mentioned that he had found beautiful micro- 

 scopic crystals of Silica, in limestone obtained from the 

 " Blue- John " mine, at Castleton, Derbyshire. He had found 

 them also in the stalactites of the same cave. He had ex- 

 amined other specimens of limestone, but had only found 

 Silica in the white varieties. The yellow colour of some forms 

 of limestone was due to an admixture of clay; the black 

 colour to an admixture of carbon in a minute state of division. 

 Where the grain of the limestone was very fine, the crystals of 

 Silica were small and perfect ; where the grain was coarse, the 

 crystals were larger and appeared corroded. He considered 

 that the presence of these crystals in stalactites and limestone 

 afforded proof that Silica was soluble, to a considerable extent, 

 in cold water, and percolated with it. Some animal and 

 vegetable forms had a greater affinity for Silica than others, 

 and would retain it whenever it came in contact with them. 

 It was possible in this way to account for the presence of 

 flints in the limestone formations. 



Mr. Sansom then read a paper, of which the following is a 

 remmSy — On the Characters employed by Botanists in the deter- 

 mination of Species. 



After remarking generally upon the great looseness existing 

 amongst Botanists in the selection of the Terms used in the 

 description of Species, and the neglect of characters derived 



