GEOLOGY AND MINERALOGY. 55 



sesqui-oxide of magnesia. Mosander's opinion, consequently, appears to be, by 

 far, the more preferable of the t-wo. 



(6) Certain specimens of the granular variety called Iserine, consist of FeO, 

 Ti02 and Fe^O^, STiO^. 



(7) Titaniferous Iron in regular octahedrons is unknown. The amorphous 

 masses and imperfectly-octahedral grains which contain titanium, appear to be 

 mixtures. 



(8) Crystallized Magnetic Iron Ore does not contain titanium. It consists of 

 FeO+Fe'^03. 



(9) All the Elba specimens of Specular Iron do not contain titanic acid ; but 

 these specimens, as -well as the specular iron from Vesuvius, always contain FeO 

 and MgO. 



(10) The strongly-magnetic octahedrons (accompanied by rhombohedral iron- 

 glance) from Vesuvius, hitherto looked upon as octahedral sesqui-oxide of iron, 

 contain a large amount of magnesia in some specimens, and protoxide of iron in 

 others. They consist either of l^agnetic Iron Ore, partly changed into sesqui- 

 oxide and combined with the isomorphous compound MgO, Fe^O^ ; or, and more 

 probably, the two monoxides are isomorphous with the sesqui-oxide of iron ; and 

 this latter is, in itself, dimorphous, 



NEW FORM IN THE CRYSTALLIZATION OF HEAVY SPAR. 



The museum of the University of Toronto possesses a crystal of Heavy 

 Spar (BaO, SO 3) from Auvergne, in which we have detected the presence of the 

 side polar or brachydome f P, hitherto, we believe, unnoticed. The crystal in 

 question is made up pi'incipally of the front and side polars -J P and F, with a 

 slight development of the basal form, B ; or, in Dana's notation, of -J i, i, and o. 

 The new form lies, of course, between P and B; and it exhibits a series of hori- 

 zontal striae parallel to the combination edge of these ; or rather, perhaps, parallel 

 to that of P and ^ P, but the latter form is not present in our crystal. The new 

 form measures, by hand goniometer, 84° 30' over the base. The strise prevent 

 the application of the reflective goniometer. Taking the three axes (a, d, a,) 

 in the protaxial form of Heavy Spar, to be as 1.135 : 1 : 0.8141 — axis d, in the 

 form I P, should be to axis «, as 1:1.095. The latter (omitting seconds) 

 == cot 42° 24' ; making the angle over the base = 84° 48'. The symbol P 

 used in this notation, has no reference to Naumann's symbol. It merely indicates a 

 polar or pyramidal form, of which there are three general kinds : Front polars, 

 niP ; polars, mV and m ?m ; and side polars, mP. In like manner there are three 

 general kinds of vertical forms: front verticals, V; verticals, Vm; and side 

 verticals, V. Besides these polars and verticals, we can only have the basal form 

 B, parallel to the horizontal or secondary axes. 



E. J. 0. 



