DOMAIN V. CALCAREOUS. 



In his edition of Linnaeus, Gmelin has produced 

 various minute substances, while he ought to have 

 begun this genus with his sixteenth species, as the 

 most important, being the Quadrum, celebrated as 

 he says in architecture*, The venerable Wal^ 

 lerius has with more judgement, as usual, de- 

 scribed the quadrum; so called, as he says, be- 

 cause it often rises in square forms. He esta- 

 blishes its calcareous nature ; and says that it is 

 of great use in architecture. He mentions the 

 white, the yellow, the grey, and the red, the latter 

 being from Shropshire. Pott, Vogel, and others, 

 at first supposed this stone to be merely cal- 

 careous, and even the sand may in fact be cal- 

 careous; but in general, upon leaving a small 

 fragment in the nitrous acid, the quartzy sand will 

 become visible or tangible. A useful observa^ 

 tion is, that the nearer to the sea it is quarried, 

 the less it will withstand the weather ; as any 

 saline particles attract the humidity, which during 

 frost expands and splits the stone. In like manner 

 if konite be accidentally moistened with sea-water, 

 }t will be subject to decay. 



In the passage of Fours, near the mountain of 



* He ranks it among the calcareous, though by his description it 

 must be argillaceous. The cement is, however, sometimes of marl, 

 or a mixture of lime and clay. 



