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s° 



T H 



NAT 



R A 



R 



i. 



5°. LYDIUM 



Touch-Jlone. 



The touch- ftone. 



vel nigricans. 



\ 





- 



2. Subgrijeunt, vel virejcens* 

 The thunderbolt-ftone, x 



3. Atro-cceruleum. 









* 



1 



^ 





4. Subcaruleum feptis divifunu 



X. 





The Touch- ftone is not of fo fmooth a grain, nor capable of fo fine a polifh as 

 either the peble or the porphiry j nor does it yet run into an open rough grain : it is 

 very hard, gives fire freely with fteel, and eludes the action of the acid, and the fire 

 with eafe. 



Soli diu fcula , particulis pellucidis arenojis aqualibus. 



« 



< 



• 







6 



O 



COS 



Grain-Jlone, 



Salidiufcula, particulis arenojis quart zofis inaqualibus. 

 Solidiufcula borizontalis, fuperficie undata, particulis 



majoribus arenojis, 

 Mill-ftone. . 



; Solidiufcula porofa dquam tr an/mi t tens 



Water- ftone. 

 5 . Friabilis, particulis glerojis. 



• 



Grinding-ftones. 



! 



The ftones of this kind are eafily known by their hardnefs and granulated appear- 

 ance: they give fire with fteel, and elude the action of the acid with eafe j nor do 

 they ever fail to anfwer the characters of the clafs in regard to the fire, though their 

 more open texture expofes them to its augmented action. 









U Va 



( 



j 



T. 



■ 



VII. 





r 



■ ■• < 



- U- 



* 4. 



+ 



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%* 





De margd SaP margaceis 







Of Marl, and the more compound Produ&ions of a 



w 



marly Nature. 



W 



H O E V E R has obferved the eafe wherewith the difft 



• 



reductions of 



this clafs, yield to both the acid and the fire ; and how readily they are, in fome 

 ftates, difunited by water; will certainly allow them to be very different in their 

 nature from thofe of the other clafies. The fubftances of this kincl are feldom of 



very ftrong 



though frequently of a fine pore and fmooth grai 



ment with acids in every ftate, and feem to be the bafe of moft of the 



but never do give fire with fteel. 



(J k 



The moft fimple Bodies of this fort 



they fer 



ene falts 





I 



Such as have not yet gone through any change ; but remain in that lefs cohe 



five form, in which they are naturally obferved in the bowels of the earth 



1 



MARGA 



Marl. 



Spongiofa ericea 

 Subfoliaa albida 

 Chalk. 



• 



Argillacea friabih 

 Marl. 







The Marl, like the earth and clay, appears to have its various degrees of admixture 

 and compofition -, and thefe ftill feem to approach the neareft to the fimple ftate that 



nfparent form, or nearly fo ; and may be considered as the 



fii 



themfi 



in a 





more immediate produce of fome fluor of this nature, which we fhall now call JL 



peuueidus calca 



the real exiftence of which is, I think, evident from the va- 





1 



ftates and appearances of many prod 



of this fort, that are daily met with 



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