4 20 Second Appendix. canos, but alfo tufas, fcoriae, and porous lava. Ibid. 224. ^ And alfo tripoli and pouzzolana. Superficial combuftions are not uncommon, and produce fingular effetfs, which have often been miftaken for thofe of true volcanos. Among others, columnar argillaceous iron ore, flates converted to llaggs, and others, with vegetabk impreffions. C H AP. III. Of the Diftindlive Charadters of Volcanic and Neptunian Mountains. Thefe are taken froni the form and arrange- ment, or from the nalure of the materials of which thefe mountains are formed. Thepeculiaritics of volcanic mountains are, ift, Tbat they ftand fingle and unconnedted, are of a conic form, and are furnithed wirb an opening of the fhape of a funnel, or inverted cone called the er ater. 2d, A total abfence of .ftratification ncar the crater, for here the volcanic cindeis, fcoriEe, and alhes mixed with fulphur and indurated, lie in confufed heaps. 3d, A firatification, where any is found, pe- culiar to volcanos, that is unequally diffufed and confufedly arranged; for this tfratitication, fuch as ir is, arifes from the liquid matter ejedted by the volcano at different'periods. Now, at each period the matter gradualiy cools as it defeends; 2 nonc