524 Dr. Mac Culloch on Ves-etahk remains 



o 



that of conferva asgagropila, although its size is such as to preclude 

 it from belonging to this species, not to notice the other important 

 distinctions between them. 



7. The seventh figure exhibits the decided character of a moss, 

 and probably of a hypnum : I have selected x.\^o of the most entire 

 branches, the greater number having the leaves folded and con- 

 fused, as if by external force, a circumstance in itself important. 

 Fibres, appearing to be those of a conferva, may be observed in the 

 same stone, which is a transparent chalcedony, with the mammil- 

 laled appearance that determines it to have been a stalagmite. 



8. A larger specimen of a plant very like No. 6. 



9. Verv delicate fibres of chlorite, but much resemblins; the 

 conferva tortuosa. They were ascertained to be chlorite by the 

 chemical means already described. 



10. The pale colour which surrounds the dark line in this figure, 

 appears to arise from some metallic crust, investing a simple fibre. 



11. In this figure nothing but a reticulation of minute yellow 

 fibres can be discerned, and it is to a similar disposition of fibres 

 that a great proportion of the red and yellow agates owe their 

 colour. I believe that this particular description of agate has never 

 been suspected to contain vegetable fibres, nor to owe the dispo- 

 sition of its colouring matter to the effect of these fibres in modify- 

 ing the deposition of iron. The agates of this tribe generally 

 exhibit a muddy uniform yellow colour ; at times, though more 

 rarely, a lively red, and are very common among lapidaries. It 

 is only when in thin plates, and by the assistance of transmitted 

 light, that the existence of fibres is detected in them. When sub- 

 jected to the action of sulphuric acid they blacken and decompose 

 it in the way I have before described. 



12. This figure is intended to convey a notion of the mode in 

 which oxides of iron invest the vegetable fibre. 



