jo A SYSTEM OF 



The First Order. 



The Calcareous Kinds, Terr* Calcare*. Thefe, 

 when pure, and free from heterogeneous mat- 

 ters, have the following qualities common to 

 them all : 



i. That they become friable, when burnt in 

 the fire, and afterwards fall into a white 

 powder. 



2. That their falling into powder is promoted, 

 if, after being burnt, they are thrown into 

 water, whereby a ftrong heat arifes, and a 

 partial folution. 



3. They cannot be melted by themfelves, or 

 per /<?, into glafs in the ftrongeft fire. 



4. When burnt, they augment the cauilicity 

 of the lixivium of potafhes. 



5. They are dhTolved in acids with effervef- 

 cence, in the following manner : 



tf. The acid of vitriol partly unites with 

 them, and forms a precipitate, which is 

 a gypfeous earth, and partly moots into 

 felenitical cryftals with that which is kept 

 diffolved, after a due evaporation. 



convex furface metals take after being melted, is a quality 

 not particularly belonging to them, becaufe every thing that 

 is perfectly fluid in the fire, and has no attraction to the vef- 

 fel in which it is kept, or to any added matter, takes the fame 

 figure ; as we find the bcrax, falfufibile micrcco/micum y and 

 others do, when melted upon a piece of charcoal : therefore, 

 with regard to all that has been faid, it is hardly worth while 

 to invent fuch definitions as fhall include feveral fpecies at 

 once ; we ought rather to be content with perfectly knowing 

 ?hem feparately : however, as this is to be an Eflay towards 

 form'ng a Syftem, I have endeavoured, in molt parts, to fol- 

 low the ufual rales. 



k With 



