5°4 CALC GENUS. Very eafily frangible. Not particularly heavy, approaching to light. Geographic and Geognostic Situations. It is found in great mafles. in the vicinity of the hot fprings at Carlfbad in Bohem a. According to Wer ner it is formed in the following manner: Particles of fand appear to be railed in the water by means of air bubbles, and become covered with calcareous earth, which is depofited around them in lamellar concretions; at length the globular concretions thus formed acquire fo much fpecific grav-ity that they fall down, and being agglutinated give rife to peaftone. What renders this explanation very probable is the almoft conftant occurrence of pat ticles of fand in the middle of the globular concretions Sometimes, but that is a rare cafe, the interior of the concretions filled with air. FOUR'tf?
