As to the mineralizing matter, it is evidently silicious, and the specimens are principally the holzstein of Werner; crystals of quartz are apparent in the cavities; some parts are agatized, and veins of chalcedony occasionally pervade the fissures: they are not impressible by steel, and give fire with it. According to the information of Mr. Perit, they are scattered over the surface of the Island of Antigua, with a profusion hardly less than that which Horneman observed of the same mineral during his travels over the eastern part of the great African desert. It is much to be wished that our numerous intelligent navigators and travelling merchants would, in imitation of this and of a similar example, mentioned below, bestow some share of their attention on the natural productions of the countries which they visit. In this way they might, on their return, render very essential services to the science of their own country. ART. VII. _Porcelain and Porcelain Clays._ Through the kind offices of a friend, we have been furnished, from one of the great porcelain manufactories in the vicinity of Paris, with a series of specimens, to illustrate the elegant art of fabricating porcelain. The specimens begin with the raw materials, and exhibit them in all their principal stages of advancement up to the perfect vessel, including the materials for the glazing, and the colours for the painting, and the application of both. At the request of the manufacturer, through whose liberality we were indulged with this gratification, we transmitted to Paris various specimens of American porcelain clays. This gentleman has caused them to be subjected to trials in the porcelain furnaces, and he finds that some of them are equal to the French porcelain clays, and some superior. As our specimens were all labelled with the names of the places, in this country, from which they were obtained, we hope soon to learn where to look for porcelain clays, equal or superior to those celebrated ones from which the superb French porcelain is manufactured. As this subject is one of much practical importance to the rising arts of this country, and as much interest has been excited in Paris concerning our porcelain clays, we should feel greatly obliged by the transmission to us of any specimens of American porcelain clays, with memoranda of the place, the quantity, the depth at which obtained, the difficulty of obtaining, and, generally, all the peculiar circumstances. We will take care that their value shall be ascertained, if they appear promising, and a proper return shall be made to the proprietor.