t& A SYSTEM OF 



SECT. XfcIL 



Observation on Clays in general. 



Thofe who have taken upon themfelves tq 

 examine the mineral bodies according to the 

 principles upon which this Syflem is built, will 

 readily, I hope, excufe thofe faults which may 

 have been committed in clafling the clays ♦, be- 

 caufe they muft well know, not only how diffi- 

 cult it is to procure a number of different va- 

 rieties of this order in their natural ftate, which 

 have not been previoufly wafhed or prepared for 



while I have in dry fummers obferved on the fea ihore, that a 

 perfect iron vitriol has been growing out of the mud, clays, 

 and vegetables not yet rotted, which has been thrown up 

 there together. 



When this opinion is once proved to be true, one may ven- 

 ture to go farther, and endeavour by obfervations and ex- 

 periments to prove likewife, that in the fubverfions or changes 

 that the earth has more than once fuffered in every part of it, 

 and in which water has contributed the moll to carry off the 

 particles, and to change the ftrata, the clay has been gathered 

 together, and lodged in beds together with other fubltances. 

 Some of thofe ftrata have afterwards been indurated, by which 

 means they are turned into the above flaty and limy clays ; 

 and when they have been mixed with a great quantity of 

 vegetables, and of the inflammable fubftance, they may in 

 length of time be changed into pit-coal : but when they have 

 been mixed with lefs phlogifton, and a great quantity of the 

 vitriolic acid, they conflitute the alum ores, &c. 



Others of thofe Itrata, which are not yet hardened, prove 

 .dill, by their being fet or divided with fome feparating veins 

 <jf fand, that they have been formed in the fame manner as 

 the fettlings or fediments of ftamping mills, and may perhaps, 

 through edulcoration in water, or through age, have loft their 

 fertility, fince they never are ib good to improve lands with, 

 • as thofe flraa which are fuppofed to be of a more recent for- 

 ■ illation, fuch as b. c, d. 



ufc 3 



