24 



The lower figure represents it as found near Kennington 

 and Lambeth, where it is common about a foot under the 

 roads in a dirty gravelly soil, partly hardened and approach- 

 ing to what is commonly called pudding-stone. It adheres 

 to the pebbles, but more particularly to the hollows where 

 they have been. In endeavouring to ascertain the nature 

 of this substance, we exposed some of the purest of the first 

 sort to a gentle heat, which soon deprived it of the blue 

 tint, emitting a sulphureous exhalation, with a blueish 

 flame, and left a dark ochry brown substance, which proved 

 to be an oxid of iron. We could not detect any prussic 

 acid by the usual method. 



Mr. Kirwan says, its colour, in its native situation, when 

 not exposed, is white. This may sometimes be the case, 

 but ours was blue even when fresh gathered and first 

 broken. 



Lustre none. Fracture dusty, of the upper figure ; 

 earthy and compact in the lower. Water does not change 

 the colour ; oil darkens it. 



Klaproth thought this mineral contained phosphorus, but 

 Mr. Kirwan thinks " the inflammability of this substance 

 must proceed from some other principle, most probably 

 carbon, perhaps an astringent substance." 



