MINERALOGY. 99 



SECT, XCL 



B. Indurated. 



1. Pure. 



a. Grev flaty, 



b. Red flaty, from Kinnekulle, in the pro- 

 vince of Weftergottland. 



2. Mixed with phlogifton, and a great 

 deal of the vitriolic acid. See Alum Ores, 

 Seel, exxiv. 



3. Mixed with lime. See Lime, SecT:. 

 xxviii *. 



* It is probable, although it \% not eafily demonflrable, that 

 the common clay, and efpecially the blue, grey, and pale 

 red, which are the foils of our plains and dales bordering 

 upon lakes, has its origin from mud, and that the mud owes 

 its exigence to vegetables ; confequently that thefe varieties 

 of clay are nothing elfe than a mould, or humus ater, fome- 

 what altered by means of water, and by length of time. 

 The following circumstances contribute greatly to confirm 

 this opinion, viz. that a great quantity of fea-plants rot 

 every year in the lakes, and are changed into mud ; that very 

 little, however, of this mud is feen upon the ihores after the 

 water is dried in fummer-time j and that the clay begins where 

 the mud ceafes. Concerning the turf, or peat, it is to be 

 obferved, that this is hot always produced from vegetables 

 growing upon the very fame fpot where it is cut, but from 

 fuch vegetables as have been thrown together from other 

 places : for in what other manner could hazle-nuts occur in 

 the turf moors, in places where no hazle-trees grow, even 

 at a diilar.ee of many miles ? not to mention other inftances 

 of the fame nature. Secondly, the turf, or peat, is cut in 

 humid and low marines, which are not conltantly covered 

 with water, as on the banks of lakes over-grown with grafs. 

 If the origin of turf was any other than here mentioned, 

 there ought to be turf found inftead of mud at the bottom 

 of lakes where there is plenty of grafs. 



The quantity of iron, and of the vitriolic acid contained 

 in this clay, would perhaps not be found greater than to an- 

 fwer in proportion to the quantity of each of thefe fubftances, 

 that enters into the compofition of vegetables, whilft growing, 

 . there Were any p )flibility of making the comparifon. Mean 



H 2 while 



