Scientific Infellijence-^Minerahffp. 191 



the same mineral species. The meUilite occiu-s in the basaltic rocks 

 of the neighbourhood of Rome, and chiefly in the quarries of Capo 

 di Bove ; sometimes in the form of imbedded grains, and sometimes 

 as crystals lining drusy cavities and fissures. It is associated with 

 augite, nepheline, Breislakite, calcareous spar, and a capillary mi- 

 neral, which has not as yet been properly examined. Its colour is 

 honey-yellow and dark brown ; it is semitransparent ; its frac- 

 ture is conchoidal, with a vitreous shining lustre; the crystals are 

 rectangular four-sided prisms, and are never more than a line in 

 diameter. It scratches glass feebly ; and its specific gravity is 

 2'95. The following is its chemical coraposition : — 



Honey-yellow Crystals. Brown Crystals. 



Silica, 39-27 3S-34 



Lime, 32-47 32-05 



Jlagnesia, .... 6-44 6*71 



Potash, .... 1-46 1-51 



Soda, 1-95 2-12 



Oxide of Iron, . . . 10-17 10-02 



Alumina, .... 6-42 8-Gl 



Oxide of Manganese, . . ... trace. 



93-18 99-30 



The Humboldtilite occurs in the blocks of Munto Somma, and has 

 the same crystallographic form as the mellilite. It is associated 

 with black augite crystals, is of a light-yellow colour, and in its 

 other characters is similar to mellilite. Its specific gravity is 2*90 ; 

 and its crystals, which are generally coated with a thin earthy cover- 

 ing of lime, and are larger than those of the mellilite, afford traces 

 of cleavage in the direction of the terminal plains. The following 

 is the result of M. Daniour"s analysis : — 



Silica, 40-69 



Lime, 31*81 



Magnesia, 6-73 



Potash, . . . . • 0-36 



Soda, 4-43 



Oxide of Iron, .... lO'SS 



Alumina, .... 4-43 



98-35 



It is proposed by M. Dumour to unite these two substances under 

 the name of Humboldtilite. — (Ann. do Chim. et cle Phys. ; and 

 Leonhard und Bronn's Jahrhuch, 1844, Heft 5, p. 592.) 



17 . New Analysis of Ferowskite. — This mineral, whic'.i was first 

 described by Professor (i. Rose, and which we formerly noticed in 

 vol. xxix., p. 418 of this Journal, has now been fully analysed in 

 the laboratory of Professor Henry Rose, by Dr Jacobson, and by Mr 

 Brooks of Manchester. The following is its composition, as deter- 

 mined by the latter gentleman :— 



