Natural History. 153 



inade, that the number of species now known is 

 between seven and eight thousand. Seven new 

 kinds of earth have been discovered within the 

 tentury under consideration. Among these are 

 Magnesia, by Hoffman and Black; Barytes, by 

 ScHEELE and Gahn; Strontites, by Hope; Silica, 

 by Pott; Alumina, by Margraaf;" Adamanta, 

 by Klaproth; and Jargonia, by the same great 

 mineralogist. Within this time, also, teii new ??ie- 

 tallic substances have been discovered, viz. Cobalt, 

 by Brandt, in 1733; iV/cZ:^/, by Cronstedt, in 

 1751 ; Platina, by Scheffer, in 1752; Manganese^ 

 by ScHEELE and Gahn, in 1774; Tungsten, or 

 J'F6>Z/7*a??2, by D'Elhuyart, in 1782; Molijbdenumy 

 by HiELM, about the same year; Uranium, by 

 Klaproth, in 17S9; Titanium, by the same phi- 

 losopher, in 1795; Tellurium, or Sylvanite, also by 

 the same, in 1797; and Chromum, by Vauquelin, 

 in 1798. — Besides these, the discoveries belonging 

 to almost every class, order, and genus in mine- 

 ralogy, have been more numerous than our limits 

 admit of recounting. 



It follows, as a natural consequence, from what 

 has been stated, that collections of minerals have 

 been more numerous, and more complete, during 

 the last century, than ever before. Among those 

 who have formed these collections, it is not easy to. 

 select such as are most worthy of notice. In gene- 

 ral, the great systematic writers, whose names have 

 been mentioned, are entitled to the highest praise- 

 in this respect also. The best collection now on 

 earth, if we may rely on the judgment of Mr. 

 Kir wan, from which few wilJ presume to dissent, 

 is that made between the years 1782 and 1787, 



n It is not meant to be aeserted that siliceous and argillaceous earths were 

 unknown previous to the time of Pott and Margraaf, but that the 

 discovery of their characters and properties, as />*/<? earths, is to be attri- 

 buted tQ tbesq mineralogists, 



