240 Canadian Record of Science. 
directly as the condensation, or inversely as the value of v. 
This may be seen in comparing colourless ordinary phos- 
phorus, v=17'2, with the metalloidal form, v=13:2; the 
isomeric silicates, meionite, v=6'5, and zoisite, v=5°3; or 
calcite, v=6'2, with dolomite, chalybite and diallogite, 
v=5'2, and with magsenite and smithsonite, v=4°7; for 
aragonite, v=5'55. These examples will serve to show the 
relations between sensible characters and chemical consti- 
tution, the interdependence of which must be taken into 
account in a natural system of mineralogical classification. 
The differences in hardness and in solubility of the different 
species just named are familiar to chemists. The behaviour 
of native silicates with fluorhydric acid, lately studied by 
J. B, Mackintosh, illustrates in a striking manner the rela- 
tions between condensation and solubility. 
S 5. The successive forms imposed upon matter gives us 
the order in which such a system of mineralogy should be 
built up. First, the form which we may call the chemical 
form of the species, either elemental or compound, due to 
the unknown stochiogenic process, or to subsequent chemi- 
cal metagenesis. Second, what may be called the mineral- 
ogical form, which involves the greater or less intrinsic con- 
traction (polymeric condensation) of the normal chemical 
species—often gaseous or volatile, but frequently unknown 
to us—and the assumption by it of a liquid or solid state, 
having greater or less specific gravity, hardness, fixity and 
insolubility, and being metallic or non-metallic, colloidal or 
erystalline. Third, the crystalline form, being the geometric 
shape assumed by the crystalline individual, which connotes 
a certain structure, apparent in the cleavage, the varying 
hardness, and the thermic, optical and electrical relations, 
of the crystal, but is, notwithstanding its value in determina- 
tive mineralogy, the least essential or most accidental form 
of the mineral species. The significance involved in the note 
of metallicity is very apparent when we consider the metal- 
lic and non-metallic conditions of selenium and of phospho- 
rus, the similar dual conditions of the sulphide of mercury 
and antimony, the non-metallic and sparry characters of the 
