EARTHS, CALCAREOUS. 22. Marga. 97 
Common in fpongy places, and may probably have Its origin in 
the rotten roots of plants: it takes a long time in drying, and 
is a bad foil for the farmer or gardener, bccaufe in the fpring 
ieafon it intumefees by the frolt at night and the heat by day, 
and lifts up and eradicates the fmaller plants. 
Very light, not combiiftible, black when moifl:. 
Hum. veget. palud. Sjsf. nat. xii. 3. p, 210. n. 7. 
Hum. acerof. palult. Wall. fyft. min. x. p. ig. ». 5. 
Humus lacuftris. Cronft. min. fedl. 293. B. 2. 
Found in fivamps and marlhes under water, and is produced by 
the gradual corruption of bog-plants: it is fo light as to re- 
main foide time fufpended in water, and is ferviceable in 
fandy foils. 
With a metallic tinge. 
Humus colorata. Wall.fjst. min. l./. 16. «. 2. 
Zyst. nat. xii. 3. /). 21 1. n. 8. to. 
Found in various parts of Britain, Snuedeiii Germany, Syria, &C. 
in fwamps and marfhes, yellow-brown, reddilh, purpliih, or 
black, which colour it receives from its contamination with 
oxyde of iron. 
f‘^eg. 
Black, becoming foltd as it dries. 
Found in Scania, often in the cultivated lands, and requires a 
peculiar method of agriculture. 
"’’"‘‘atica. 
Brown, of a faltifli taftc. 
Argilla muriatico-falfa. S^iji. nat. xii, 3. p. 205. n. 20. 
Terra e palxliina. Cronst. min. p. 123. 
Found in the defarts o;i the confines of the Red-fea, Egypt, ani 
Syria, 
22. MARGA. Confining of carbonate of lime and 
argil, with generally lome oxyde of iron: foft, 
opake, of a common form, internally earthy, 
light and inifcible with common water by agita- 
tibin, found in (iratitied mountains : partly folu- 
ble in nitric acid, with effervefcence : hardening 
in the fire, and vitrifying in a ftrong heat. 
Friable, meagre, a little rough to the touch. 
Argilla mixta. Syst. nat. xii. 3. p. 204, n. 17. 
Marga friabilis. Cronst. min. p. 26. 
Argilla rudis. Garth, min. (>, 
Calcareous Marl. Kii~M an miner, 94, 
F.arthy Marl, Schmei/Jer miner, i. p. 228. 
VOL, VIl. — N 
