NATURAL HISTORY. 



by which they are called ' Matter/ as Solidity, Fluidity, Vapour, Form, 

 Weight, so as to become the immediate object of the senses : but all 

 Matter has properties abstracted from those which may be called the 

 specific properties by which one species of matter is distinguished from 

 that of another — the knowledge of which arises from investigation ; 

 which [properties] may be called ' secondary,' some having one, two, or 

 more secondary properties, others having others, all having some, and 

 many of these secondary properties being more confined, not being 

 common to all matter. It is therefore ' secondary properties ' that in 

 some degree distinguish one kind of matter from another. Two solid 

 bodies may have the same solidity, form, weight, &c., yet [consist of] a 

 very different species of matter from each other — for instance, crystal 

 and calcareous earth may have the above properties in common with 

 each other, yet differ very much from one another in many other pro- 

 perties. 



When they are to undergo some change, one will not be affected by 

 any acid, while the other is totally dissolved, which becomes one dis- 

 tinguishing mark between these two substances or species of matter. 

 But, although dissolving in an acid is one characteristic of calcareous 

 earth, yet it must have others to distinguish it from other earths that have 

 the same property of solution in an acid. Magnesia [e. g. so resembles 

 calcareous earth], but its forming a selenite with the vitriolic acid makes 

 a distinction. But, perhaps, the true character of calcareous earth is, 

 its affinity to animal and vegetable substances, when simple; although 

 this last property is not peculiar to this earth, for alkalies are endowed 

 with the same. Alkalies have properties that the calcareous earths 

 have not, by which they are distinguished from one another. So that 

 its forming a selenite with the vitriolic acid and its reunion with the 

 vegetable and animal substances become its specific property, while its 

 solution in an acid in general was only its specific property in the 

 second degree. 



The same observation holds good respecting fluids : for two fluids 

 may have the same fluidity, specific gravity, &c., yet be very different 

 in their other specific qualities. Water is a fluid, so is oil of turpen- 

 tine, spirits of wine, &c, but their specific properties are very different. 



Many earths are vitrifiable, others not ; however, such as are veri- 

 fiable have other properties by which they are better known than by 

 their vitrifaction or not — by which they are distinguished — the vitrifac- 

 tion being only considered as a collateral property. 



Is it possible for an absolute existence to be mutable, or in other 

 words, is anything that is really existing changeable ? I should be in- 

 clined to believe that whatever does exist or can exist is not changeable. 



