156 ON COLOURING GEOGNOSTICAL MAPS, 



tion-suite, will be red shaded into blue, the blue 

 into grey, and this latter into green, and the 

 green into yellow, — The inflammable-fossils, su- 

 bordinate to these formations, will be dark-brown. 

 —The limestone- formation suite, will be blue, 

 which will pass into grey, and lastly into white. — 

 The salt and gypsum formation suites, which are 

 allied to the preceding, will be greenish-blue, 

 and bluish-green. — -The trap-suite, greenish-black, 

 and blackish-green, shaded into blue. — The por- 

 phyry-suite, light-brown. — The talc and serpen- 

 tine suite, pale yellowish- green. 



Such then is the method of representing by 

 means of colours, the different rocks of which a 

 country is composed : we have now to point out 

 how their relative positions are to be deline- 

 ated. These are most satisfactorily and simply 

 expressed in the following manner, as first pointed 

 out by Werner : Boundaries of superimposed 

 rocks, are to be marked with a broad line of the 

 same colour as the rock, only darker, and in those 

 cases where we are uncertain as to the superpo- 

 sition of the rock, the junction is to be merely 

 streaked. Beds, when they appear at the surface, 

 should have their boundaries distinguished by a 

 broad but darker line of the same colour as that 

 of the rock of which they are composed. When 

 the beds are inclined, the lower side should be 

 marked with a broad line of the same colour as 

 the bed itself, but its upper-side by a broad dark 

 line of the colour of the rock that rests upon it* 



