OF THE MAP. 



DESCRIPTION OF THE MAP, IN REFERENCE TO 

 USEFUL MINERALS. 



Slate Colour. No. 1, 2, 3, 4, 5. 

 This colour indicates the formations, which contain beds 

 of carbon. These beds are, 1. Carburet of iron (plumbago) 

 2. Jlnthracite^ (coal without bitumen,) 3. Cr?«Z, (containing bi- 

 tumen,) 4. Coal of a sulphurous character, (containing iron py- 

 rites,) 5. Lignite, (presenting the form of wood.) 



Yellow colour. Quartzose formation, less useful than 

 the other two formations. When this rock is divided into 

 blocks, by natural cleavages, (as granular quartz in most ca- 

 ses,) it is used for quarrying ; otherwise it is not used on ac- 

 count of the labor of cutting. In some localities, these rocks 

 are red and sandy. They are then wrought under the name 

 of freestone. Saliferous rocks belong to this formation, but 

 they are placed under the red colour. 



Blue colour. Carbonate of lime (limestone, pure carbon- 

 ate of lime, or more or less silicious.) The compact is always 

 useful, as marble, under the names statuary (granular,) birds- 

 eye (with nt'arly verticle encrinites,) or varigated, (when its 

 colours are mottled, whether statuary, birdseye, or amorphous.) 

 All kinds of limestone may be manufactured into mason's lime 

 by burning. If a large proportion is quartzose, it makes an 

 indifferent hydraulic cement. The genuine hydraulic cement 

 (water limestone of Engineer C. White,) should contain a pro- 

 portion of iron and magnesia. 



Red colour. Sand-rock or marl-slate. These rocks are 

 hard and silicious, or soft and slaty. They are always red or 

 bluish grey. They belong to the quartzose formation of the 

 third series, but they are of sufficient importance for a distinct 

 colour. All the salt springs of North America are in this 

 rock ;* and all the American basalt rests on it. 



* The Licks of muriate of lime and soda do not belong to this formation ; 

 but are often found in transition districts, &c. 



