John MacCulloch

“ The limited number of the specimens which I possess, and the obscurity which attends not only these remains but the present living species, prevents me from attempting an answer to this question on botanical evidence, and on my own knowledge. But the observations of Daubenton appear sufficient to decide that in some instances at least they consist of existing species. Since too the formation of flinty matter by deposition from water is a daily occurrence, there is no reason to doubt that they may be specimens of plants now actually existing. ”

“ In many others no mechanical texture or disposition can be discovered in the stone, but the whole appears one semitransparent mass of chalcedony. These are the specimens in which the confervæ preserve that freedom of arrangement and that perfection both of colour and structure which seem to imply that they had been so suddenly involved in a mass of siliceous matter as to have been preserved from all future changes. Many other specimens have that mixed aspect of jasper and chalcedony to which among other varieties of ornamental stones the lax term of agate has been, applied. ”

“ 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 disposition of its colouring matter to the effect of these fibres in modifying 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. ”

“ Similarly contorted fibres occurring in chalcedony do not exhibit the crystallized structure, but appear to consist of very minute or of invisible particles, or even of a mere colour diffused in that particular form. At times the coloured fibre contains grains of chlorite attached to its sides or interspersed through its course, thus emulating the imbedded seeds or jointed appearance of real confervæ, and I have reason to think often mistaken for them. ”

“ Numerous red, white and yellow agates are every where to be found among collectors and dealers, in which the appearance of fibres is such as to render it very probable that they are portions of vegetables incrusted by oxides of iron, although the obscurity of the specimens must necessarily render this uncertain until they are submitted to chemical trials. ”

“ In these specimens (brought from Egypt) distinct grains of green matter may be observed independent of the general green stain which pervades the stone; and this probability is rendered still stronger from the colour and appearance which is occasionally assumed by the more transparent flinty matter associated with the chalcedony, the latter acquiring from the chlorite the aspect of heliotrope, while the more transparent parts put on the semblance of plasma. But of a substance so rare it is necessary to speak with hesitation. ”

“ At times however the fibre assumes a whitish aspect, or the yellowish and reddish hue which those delicate plants exhibit when dead, an appearance perhaps even more characteristic of their vegetable nature than their natural colour, since we cannot easily understand how it could be imitated either by chlorite or by metallic oxides. ”

“ It is besides known to botanists, that many plants possess the property of attracting from their state of combination the earthy base of some of the salts which are dissolved in natural waters, a property which may be subservient to some purpose in the economy of the plant, unknown to us. ”

“ The eye of a botanist will also with care discover an irregularity in the superposition of the scales, which never occurs in the plants themselves, and a decision in the setting on of the branches in the real plants, which is ill imitated by the clumsy way in which the ramifications are disposed in the metallic arborization. ”

“ Together with these circumstances, the natural colour is often equally well preserved, and the various specimens of the confervæ in particular, which are the plants of most common occurrence, exhibit all the different tones of colour, from the most brilliant grass green to the darkest sap or lightest yellow green which at present characterize the different living specimens with which we are acquainted. ”

“ In many cases even the most scrupulous attention will fail, a fact which need excite no surprize when it is considered with what difficulty the examination must often be conducted, from a deficiency of light when transmitted through these stones, and from the impossibility of bringing into view any considerable portion of the imbedded substance. ”

“ The metallic arborizations emulating the vegetable form which occur in the fissures of many stones, and the similar well-known figures in the chalcedonies distinguished by the name of mochas, with the lively though superficial resemblance they bear to plants, have led to the hasty conclusion that all these appearances were of a metallic nature, and have probably prevented that accurate investigation of them which they deserved. ”

“ I ought however, to add, that in many of the Siberian specimens which are known to lapidaries by the name of Moss agates, I have ascertained by chemical means that the green fibres consist of chlorite. ”

“ Yet it offers some important differences which may throw light on certain disputed points, and lead to conclusions of no small consequence, conclusions not so universally resulting from those facts. It has been maintained on one hand that the silicification of wood and of animal remains might have been the result of silex injected in a state of igneous fusion. ”