444 



No. 80. Arundinis vallatorice radix*. Luid. p. ISO; but a reference 

 to the work of Lhwydd is fruitless, since its number of pages is 

 less than the number referred to ; nor do I discover the descrip- 

 tion of such a specimen. Langius presents us with a figure of a 

 Rhizolithus, of which he thus speaks : " sublutei est colons, et ra- 

 dicem pastinacce tenuifolice sativce radice lutea. Casp. Bauhin. Pin. 

 prcesefert, attains est & Toggio*^." But that the substance he thus de- 

 scribes was merely a figured stone, which had by some accidental 

 occurrence assumed the form of a piece of carrot, is most probable: 

 for no fact in the history of these substances is more true than the 

 position laid down by Wallerius, when speaking of the requisites 

 to be possessed by substances to render them capable of becoming 

 the subjects of petrifaction. " Ea," he says, " sit indole et duritia 

 ut non facile putrefactionem, vel aliam destructionem, subire pos- 

 sit, sed diutius in locis subterraneis incorrupt! bile conservari." 

 Linna3us also saysj, " Corpora petrificanda sint solida: testae, ossa, 

 ligna. Succulenta deliquescunt et corrumpuntur antequam indu- 

 rescant lapidosa." But even a modern author, justly celebrated 

 for his knowledge in chemistry and natural philosophy, speaks of 

 a petrified potatoe, a rhizolithus as inadmissible as that of Lang. 

 Argenyille, Hell wing, and others, have also described Rhizolithi; 

 and the last-mentioned author, not only speaks of them, in even 

 an agatine state, but distinguishes them into the roots of dif- 

 ferent trees. It must, however, be obvious, that the difference be- 

 tween the roots of different trees can hardly ever be such as to 

 allow of its being ascertained, to what kind of tree a petrified frag- 

 ment may have originally belonged. Thus the specimen repre- 

 sented at Plate II. Fig. 2. indubitably deserves to be considered as a 

 true Rhizolithus ; since, although it now possesses the hardness and 

 bears the polish of agate, its external form, as well as its general 



* Appendix He^barii Diluviar i, p.70. f Historia Lapidum Figurat. Helvetia, p. 54. 

 | Sy sterna Naturae, torn. iii. p. 154. 



