2S4 PHILOSOPHICAL TRANSACTIONS. [aNNO 1746. 



nated, some with calcareous and particles of other stones, and others with fer- 

 rugineous and vitriolic particles. Those of the stony or calcareous kind, when 

 they drop on wood, or other vegetables, act on them for the most part by in- 

 crustation, having different degrees and periods for their respective incrustations 

 and coalitions, which yet adhere close to each other : they seldom turn the wood 

 into stone ; but, sticking to the wood, plants, &c. coagulate on it, and by degrees 

 <x)ver it with a crust of a whitish substance of different thickness, by which the 

 wood is immerged or wrapped in a stony coat, which, if it be broken before the 

 wood be rotten, you find it in the heart of the stone or incrustation, as is seen in 

 those petrifications at Maudling meadows in Gloucestershire, at Hermitage near 

 Dublin, and many other places : or, if the wood be rotten, you will find a cavity 

 in the stone, which very often is filled by a subsequent incrustation or petrification ; 

 the stony particles then taking the place of the rotten wood. 



Sometimes indeed, these waters, permeating the pores of the wood either 

 longitudinally or transversely, insinuate themselves into them, fill them up with 

 their stony particles, swell, and, by their burning or corroding quality proceeding 

 from the lime-stone, destroy the wood, and assume the shape of the plant, the 

 place of which they have taken. 



These petrifications generally ferment with acids and spirit of vitriol, and by 

 calcination may be reduced to lime. 



Ferrugineous or metallic petrifying waters mostly act by insinuating their finest 

 particles through the pores and vessels of the wood, or other vegetables, without 

 increasing their bulk, or altering their texture, though they greatly increase their 

 specific gravity: and such is the petrified wood found in or on the shores of 

 Lough-Neagh ; for it does not show any outward addition or coalition of forcing 

 matter adhering to, or covering it (except in some places, where a thin slimy sub- 

 stance, taken notice of hereafter, is sometimes observed), but preserve the grain 

 and vestigia of wood ; all the alteration is in the weight and closeness, by the 

 mineral particles pervading and filling the pores of the wood : these stones, or 

 rather wood-stones, do not make the least effervescence with spirit or oil of vitriol, 

 nor aquafortis; which shows that they are impregnated with metalline particles, 

 or stony ones, different from the calcareous kind ; and may be the reason why the 

 petrified wood, mentioned by N. Grew,* made no ebullition, at which it seems 

 he was surprised.-^ These stones he could not reduce into lime by the most in- 

 tense fire, nor, with proper ingredients, procure a vitrification or fusion. J 



* Reg. Soc. Mus. p. 270. — Orig. t This contradicts an observation of Mr. John Beaumont, 



(Phil. Trans. N° 129). That mostly mineral stones will stir with acids ; whereas all those that I have 

 tried, whether English or Irish, did not at all stir with acids. — Orig. J Stones of the calcare- 



ous kind turn to lime by calcination, and ferment with acids j but other kinds, such as slate, fire- 

 stone, free-stone, rag, grill, &c, will do neither, as experience has hitherto testified. — Orig. 



