126 PHILOSOPHICAL TRAJTSACTIGNS. ^ANNOi 1704. 



this first sort you have doubtless many instances in Essex, and I think there is 

 one at Harwich clifF; though this is not so properly called a petrifaction. 

 2. The second sort is that which is performed by the permeation or insinuation 

 of the finer sorts of stony particles ; as is the case of some of our petrifying 

 waters, particularly that at Knaresborough ; the stony particles however of the 

 Knaresborough spring are very fine. And many of the fossil-shells have under- 

 gone the same fate. 3. The third, which indeed is a petrification, properly 

 so called, is often met with on the sides of caves and grottos, as at Pooly-hole 

 in the Peak, and in the fissures and clefts of mines and quarries. Of this kind 

 are the several sorts of fluors, the lap. stillatitii stalagmites, &c. that we meet 

 with in the fissures and hiatuses of the earth. These are continually receiving 

 an additional increase of real and solid stone, as is observed in several caves in 

 the peak, &c. This I take to be performed in such a manner as the incrusta- 

 tions are, viz. the particles of stone are brought along with the water as their 

 vehicle, and at length are deposited on the sides of the cave or fissure : but here 

 the particles of stone are extremely minute and fine, and do thereby naturally 

 concrete and join very close together ; whereas, in our incrustations, the par- 

 ticles of stone being grosser, the stone is rough-,, coarse, and friable. And this 

 I leave to your judgment, if it be not a more reasonable Hypothesis than that 

 of Dr. Plot, in p. 33, of his History of Oxfordshire, viz. That the very body 

 of the water is turned into stone as it drops down from the rocks. As to that 

 hypothesis of the transmutation of a stratum, c g. of chalk to clay, of coal to 

 common stone, or the like, I must confess I never met with any thing in nature 

 which would countenance it, that is, such a transmutation in the bowels of the 

 earth. Nor is there any thing that proves it, that ever I have met with in any 

 natural observations.** 



A late author is of opinion, that this bed of stones was the foundation of 

 the loamy cliff, v^^here the cliff has been washed away or cut ; and that they 

 are the production of a vitrioline juice, iu conjunction with the loam ; as the 

 common copperas stones are by the same juice in a gravel ; and that the latter 

 were only to be found where the cliff was gravelly, and not where the loam is. 

 How far these stones are the effect of a vitrioline juice, I will not determine ; 

 but this lean affirm, that I have now by me some of the pyrites, or common 

 copperas stones, which I picked out of the clayey stratum of this cliffy in which 

 they may be frequently met with. Nor do I remember at any time to have 

 observed these stones to be invested with either gypsum or trochitis, as the 

 same author affirms, but often with the aforesaid ludis Paracelsi, and some 

 other sorts of lapides stalagmitae. 



How those shells or marine bodies came to be deposited here, is a subject 



