On an examination of the volatile alka li, and after a great number of complex and tedious experiments, Mr. Davy saw reason to conclude that ammonia contains oxygen as an essential ingredient, and that this cannot well be estimated at less than 7 or 8 parts in the hundred : this body may therefore, as he says, be con sidered as the principle of alkalescence, with as much reason as the French have made it the principle of acidity. After making some general remarks on the preceding facts, he suggests the proba. bility, that the muriatic, fluoric, and bo racic acid all contain oxygen as one of their constituent principles. The earths of barytes and strontian, as being most ana logous to the alkalies, were likewise ex amined, and both yielded oxygen. In con cluding this very important communica tion, Mr. Davy remarks, that an immense variety of objects of research is present ed in the powers and affinities of the new metals produced from the alkalies. In themselves they will undoubtedly prove powerful agents for analysis ; and having an affinity for oxygen, stronger than any other known substances, they may possibly supersede the application of electricity to some of the undecom pounded bodies. Further experiments, it is said, have enabled Mr. Davy, since his communication to the Royal Society, .frorn which the above has been partly abridged, to decompose, in the most satis factory manner, the barytes and stronti tes, and to show that the other alkaline earths are oxides of highly combustible metals. It cannot now be doubted, that, in the hands of this great chemist, other bodies, hitherto deemed simple, or at least never yet 'analysed, *ill speedily yield to the powers either of the highly inflammable metals already discovered, or of a still further increase of the gal vanic battery. Mr. Davy has decompos
ed carbonic acid by means of those me tals, and has oxydated them by muriatic acid ; and an excellent writer says, " it is now by no means improbable that char coal itself, hitherto regarded as the most refractory of all substances, may be de composed by the new instruments ; and that the means of obtaining it pure, and even crystallized, shall at last be found ; a discovery which would enable art to vib with nature in the fabrication of her most valuable produce." At any rate, to use the words of the Professor himself: " In sciences kindred to -chemistry, the knowledge of the nature of the alkalies, and the analogies arising in consequence, will open many new views ; they may lead to the solution of many problems in geology, and show that agents may have operated in the formation of rocks and earths, which have not hitherto been suspected to exist." See Philosophical Transactions of the Royal Society for 1808. Part I.
POT stone, in mineralogy, a species of the Clay genus. The colour of this mi neral is a greenish grey, of different de grees of intensity. It occurs massive. The internal lustre is glistening and pear ly. Fracture, sometimes curved, fbliat ed, sometimes imperfectly slaty. It is soft, feels greasy, and difficultly frangible. It is found in beds with serpentine, at Como in the Grisons ; in some parts of Saxony, and in Hudson's Bay. It is very nearly allied to indurated talc. It is re fractory in the fire, and may be used for lining furnaces. It may be turned in a lathe, and made into a variety of ves sels fit for culinary and other purposes.