MINERALOGY, 
99 
SECT. XCI. 
B. Indurated. 
1. Pure. 
a. Grey flaty. 
h. Red flaty, from Kinnekulle, in the pro- 
vince of Weftergottland. 
2. Mixed with phlogifton, and a great 
deal of the vitriolic acid. See ilium Ores^ 
Sedl. cxxiv. 
3. Mixed with lime. See Lime, Sefl. 
' xxviii 
It Is probable, although it is not eaUly demondrable, that 
the common clay, and efpecially the blue, grey, and pal^ 
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 at er, fome- 
what altered by means of water, and by length of time. 
The following circiimftariCes contribute greatly to confirm 
this opinion, viz, that a great quantity of fea-plants rot 
every year in the lakes, and are changed into mad ; that very 
little, however, of this mud is feen upon the fliores after the 
water is dried in furnmer-time; and that the clay begins where 
the mud ceafes. Concerning the turf, or peat, it is to be 
obferved, that this is not 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 
die turf- moors, in places where no hazle>trees grow, even 
at a dillance of many miles ? not to mention other inftances 
of the fame nature. Secondly, the turf, or peat, is cut in 
humid and low marfhes, which are not conftantly 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 compoftdon of vegetables, whilll growing, 
if there were any poiTibility of making the comparifon. Pvlean 
H z while 
