OF CENTRAL CANADA PART I. 19 



are solid. Some few occur naturally, at times, in the free or simple 

 state. These form the so-called "native substances" (as Native 

 Sulphur, Native Platinum, Native Gold, &c.,) of Mineralogists. 

 Others occur only in combination. Some have a remarkable 

 tendency to attack and combine with other bodies. Oxygen, 

 chlorine, fluorine, sulphur and arsenic, in reference to natural 

 compounds, may be especially citecf in this respect. The binary 

 compounds formed by these elements may be more^ or less passive 

 bodies or bases, or active bodies or acids, although in some cases a 

 strict line of demarcation cannot be drawn between the two. The 

 bases have their generic name always terminated by the monosyllable 

 "ide." Thus oxygen, in forming a compound of this kind, produces 

 an oxide ; chlorine, a chloride ; fluorine, a fluoride ; sulphur, a sul- 

 phide ; and arsenic, an arsenide. Sulphur and arsenic compounds of 

 this sort were formerly known as "sulphurets" and " arseniurets," 

 but these terms have now passed out of use. When more than one 

 compound of the above kind occurs, a distinctive prefix is added to 

 the term. Thus red oxide of copper is often known as the " sub- 

 oxide," whilst the black oxide of copper is known as " oxide " simply. 

 The red oxide contains two parts (combining weights,) of copper 

 to one of oxygen ; the black oxide, equal parts (combining weights,) 

 of each element. In like manner the oxide or protoxide of iron con- 

 sists of equal combining weights of iron and oxygen, whilst the 

 the sesquioxide or peroxide has one-and a-half parts of oxygen to 

 one of iron or, as more commonly given, three combining weights 

 of the former to two of the latter element. [By some authors these 

 compounds are known, respectively, as cuprous and cupric oxide, 

 ferrous and ferric oxide the termination " ic " denoting the presence 

 of the larger amount of oxygen.] Active or " mineralizing " com- 

 pounds into which the above and other elements enter, are still com- 

 monly known as " acids," although many of these, it must be remem- 

 bered, are insoluble compounds, and hence have no acid properties in 

 the common acceptation of the term. By many modern chemists 

 they are designated as "anhydrides." For present purposes we need 

 only refer to oxygen compounds of this class. In these, the combi- 

 ning weights of oxygen are always greater than in bases or oxides 

 proper. Some elements form, with oxygen, several acids. Where 

 two exist, the one with least oxygen has its generic name terminat- 



