solidifying in a short space of time, or capable at least of suddenly gelatinizing previously to the ultimate change by which it became solidified into stone. I need not point out the extreme importance of this supposition, I had almost said of this fact, to any general theory of the earth. It is for chemistry yet to investigate experimentally the mode of imitating this unknown process. Those who know the present state of this science will not hesitate to admit its imperfections, and those who have attended to its rapid progress will not despair.
No. 1. I think the peculiar membranes and defined structure seen in this figure can only arise from a plant, although I am not acquainted with any analogous living vegetable. I had not enough to subject it to chemical trial.
2. This figure exhibits one of the most common forms in which chlorite is disposed in chalcedonies, a form not very likely to mislead an observer.
3. I have figured this for the purpose of shewing the remarkable imitation of a conferva, which may be produced by chlorite; that part of the drawing which is most highly magnified, exhibiting a chain which consists of distinct scales of this substance.
4. Is drawn from a specimen which appears to contain fragments of two plants; a conferva, and the leaves of some other plant, perhaps a moss.
5. That this drawing is made from a plant, I have ascertained by chemical trial, and the green spots which seem disseminated along the fibre are probably the fructification.
6. This specimen exhibits an internal structure, not very unlike
3 u 2