Transactions of the Geological Society, 1st series, vol. 4/Explanation of a Supplementary Plate on Vegetable Remains preserved in Chalcedony

Explanation of a Supplementary Plate on Vegetable Remains preserved in Chalcedony
by John MacCulloch

XX. Explanation of a Supplementary Plate to the Paper on Vegetable Remains preserved in Chalcedony, printed in the Second Volume of the Transactions of the Geological Society.

By the J. Mac Culloch, M.D. F.L.S. President of the Geological Society, Chemist to the Ordnance, Lecturer on Chemistry at the Royal Military Academy, and Geologist to the Trigonometrical Survey.

[Read 19th May, 1815.]

Fig. 1.[1] This figure is given for the purpose of explaining the mode in which the fibrous disposition of chlorite is effected. The crystallized arrangement which is here so visible is generally observed in those chlorite fibres which occur in transparent quartz. I I have never observed it in chalcedony, yet there is little doubt that a similar disposition is equally the cause of the fibrous appearance so common in the specimens which have been figured in the former plates, the chief differences consisting in the smaller size and less perfect crystallization of the chlorite scales.

Fig. 2. The crystals of chlorite magnified.

Fig. 3. Although in the former plates I figured some specimens which I imagined to be confervæ, I had not then procured any example in which that regularity of structure, which is so conspicuous in some of the plants of this family, could be observed. The present figure exhibits that regularity in a striking manner.

Fig. 4. This figure affords a second example of that regular ramification which botanists will immediately recognize as characterizing many of the plants of this tribe; although for the reasons already assigned in the paper, it will be fruitless to attempt to discover the species.

  1. Pl. 27.