'm \ArgtlUceous Genus, S E C T I O N IX. Argillaceous Genus. ift Clafs. 'Argillaceous Eartbs. THESE are for the moft part diffufible in water, and do not immediately fink in it as fands do ; or if fo compad as immediately to fink, they foften, crumble, or moulder away in it, fome fooner, fome later, either toa dudile vifcidpulp, or to a powder. Hardnefs, fcarce ever exceeds 6 ; they harden when heated; fcarce ever effervefce with acids, and are difficultly foluble in them. As earths'originally received their denomina- tions from external and not from internal cha- raders, they cannot now, without creating much confufion, be arranged according to their real fpecific properties, if any fuch could be affigned. But in fad none fuch can, except fufibility 01 infufibility, which depend on proportions and in- gredients both mutable and cafual. Hence I fhall fort them under the title of different Tribes; marking the cafes in which thefe are found to bc more or lefs fufible, or adapt^d to various ufes. ift Tribc.