TERRA PONDEROSA vitriolata, (heavy ſpar, marmor metallicum, calk) is placed with the earths (§ 89.) Terra ponderoſa nitrata i. e. terra ponderoſa united to the nitrous acid, perhaps exiſts ſomewhere, but has never been met with; neither has the terra ponderoſa united to the aerial acid, yet been found[[31]]. Terra ponderoſa ſalita i. e. terra ponderoſa with the muriatic acid Mr. Hielm ſays[[32]] is diſſolved in the waters of the lake Vettern and its neighbourhood.
CALX vitriolata (gypſum, ſelenite) is not only found diſſolved in various waters, but alſo in many places forms immenſe ſtrata. It is placed by all mineralogiſts amongſt the earths, but I think improperly. When burnt it generates heat with water, but in a leſs degree than lime does.
CALX nitrata (nitre of lime; terrene nitre) is ſometimes found in water, but very ſparingly. It is ſaid that the chalk hills in ſome parts of France become ſpontaneouſly impregnated with nitrous acid, which may be waſhed out, and after a certain time they will become impregnated with it again.
CALX Salita (fixed ammoniac) occurs very frequently in waters.
CALX aerata (marble, limeſtone, chalk, ſpar) is very commonly found diſſolved in waters in conſequence of an exceſs of the aerial acid. When it greatly abounds, the water is ſaid to be hard (cruda). By boiling, or by evaporation, it depoſits ſtreaks or cruſts of calcareous matter.