594 PHILOSOPHICAL TRANSACTIONS. [aNNO 1735. 



the steams, &c. which rested on the wax and glass. Which he thinks suffici- 

 ently proves the steams, &c. to be non-electric; and he thinks that it as plainly 

 appears, that they are all electrified while ascending, because the electrical fire in 

 the down does not join with them in their passage through it; which otherwise 

 it would do with them, or any non-electric not electrified. 



XXVI. Remarks on a Petrified Echinus of a singular kind. By Ja. Parsons, 



M.D., F.R.S. p. 155. 



This echinus was found on Bunnan's-Land, in the parish of Bovingdon in 

 Hertfordshire, which is a clay, and supposed to have been brought with the 

 chalk, dug out of a pit in the field. The round echinites are for the most part 

 found in chalk-pits, and they are in general, when recent, the most tender in 

 their shells; so that the chalk is the most favourable bed for them to be preserved 

 in long enough to be petrified; whereas in other kinds of matter, these would be 

 mouldered and destroyed before the petrification could commence; and it is very 

 singular, that almost all those in the chalk are filled with flint, or partly chalk 

 and partly flint, and sometimes with crystal. Now, as all flints and agates are 

 nothing else but crystal debased by earth, and as it is in beds of chalk that these 

 as well as multitudes of large stones are found, one would be almost induced to 

 believe, that chalk degenerated into flint; or, in other words, that flint was pro- 

 duced by chalk originally. And Dr. P. says he had many specimens, that seem 

 to prove it; in some of which they seem to show the gradual change from the 

 one to the other, not at all like a sudden apposition of chalk to flint. 



Other kinds of echinites, such as the echini cordati, or heart-shaped echinite, 

 the pileati or conic, the galeati or helmet- shaped, with several other kinds, are 

 often formed of other species of stony particles. But the present fossil, being 

 one of the oval kind, with large papillae, is the echinometra digitata secunda 

 rotunda vel cidaris mauri of Rumphius, which, with the other oval echinites, are 

 very rarely found out of chalk; and it is remarkable, that whether they are filled 

 with chalk, flint, or crystal, their shells break with a selenitical appearance, just 

 as the lapides judaici, and all other species of echinites found in chalk-pits, do. 



XXVII. On Toxicodendron. By the Abbe Mazeas, F.R.S. From the French. 



p. 157.* 

 The Abbe Sauvages, of the Royal Acad, of Montpellier, communicated a 

 discovery of a plant, the juice of which adheres, without the least acrimony, to 

 a cloth, with more force than any other known preparation. The colour is black, 



* The vegetables mentioned in this paper, as well as in tlie following letter by Mr. Miller, belong 

 to the Linnean genus rkui. 



