It is well known that they are volcanic, and of course afford the usual volcanic substances. The most interesting part is that occupied by the boiling fountains, in many respects similar to the Geysers of Iceland, excepting that the water is not ejected to any considerable height; but the incrustations, the sinter, and sulphur, are every way equal to any specimens which Dr. Webster saw in Sir G. Mackenzie's collection. We are much gratified in noticing both what Dr. Webster has done and is still doing. We are persuaded that he will do much towards promoting the cultivation of American mineralogy and geology, and especially in the enlightened community in which he resides. We cordially wish him success, and trust that it will be ensured by the patronage of the citizens of Boston. 3. _Supposed identity of Copal and Amber._ A correspondent, whose paper is withheld from publication till some additional experiments can be made, conceives that copal and amber are originally the same substance, and the product of the same tree. 4. THE NECRONITE.--(_A supposed new mineral._) _Extract of a letter from Dr. H. H. Hayden of Baltimore, to the Editor, dated January 5, 1819._ "It (the necronite) occurs in a primitive marble, or limestone, which is obtained 21 miles from Baltimore, and a small distance from the York and Lancaster road. It was first noticed by myself at Washington's monument, in which this marble is principally employed. "It occurs, for the most part, in isolated masses in the blocks, or slabs, both in an amorphous and crystallized state. It is most commonly associated with a beautiful brown mica, of the colour of titanium; small but regular crystals of sulphuret of iron, tremolite, and small prismatic crystals of titanium, which are rare. The form of the crystals is a rhomboid, approximating very much to that of the felspar, and which has inclined some to consider it as such. Also, the hexaedral prism, resembling that of the beryl. This form is rare, and has not, as yet, I believe, been found complete. Its colour is a bluish white, and clear white. Its structure much resembles felspar, being lamellar; sometimes opaque, semi-transparent and transparent, at least in moderately thin pieces. It scratches glass, carbonat of lime, and even felspar, in a _slight_ degree. In all our efforts, it has been found infusible, per se, or with borate of soda, and even from all the force of heat that could be excited in a smith's furnace, it came out unchanged in any degree. The acids seem to have no sensible effect upon it, either cold or hot. This is all that I can say of it at present, except that it possesses a most _horrid_ smell.[44] I have since found in a marble of the same kind, but from a different quarry, and a few miles distant from the first, a quartz almost as fetid as the necronite, and likewise associated with _small_ prisms of titanium.