OF THE VARIOUS LEAD-SPARS. 
509 
able such as are conversant with mining operations, to 
guess at those situations which are hkely to abound with 
them in greatest perfection, attracted my notice, and led 
me to bestow some share of attention on the subject. I 
was soon induced to think that the galena was the first 
formed of the minerals occurring in this neighbourhood, 
and that all the others were formed by its decomposition : 
and I am strongly inchned to think that the same will be 
found to be the case in every situation where lead occurs. 
To this conclusion I have been led by the following con- 
siderations. 
I. Galena, or sulphuret of lead, is by far the most 
abundant, and generally diffused form, under which this 
metal is found ; indeed, I may say it is incomparably more 
abundant than all the other lead-spars taken together. 
II. I have not been able to ascertain that any one of the 
various lead-spars has been found where galena was not 
either immediately present, or in the vicinity of such situa- 
tions, or had been wrought out in that quarter at some for- 
mer period. 
III. The appearance of the galena itself, in many situa- 
tions, strongly evinces the reality of the change I have al- 
luded to ; for it may be seen in every gradation of decay, 
from its being merely covered with a dusky coating in 
place of its usual metallic lustre, to that state in which the 
greatest part of it is reduced to a black, or a dark-blue or 
grey powder. 
In such situations, the cellular, or worm-eaten ore, fre- 
quently shews itself, owing to this very process going on : 
and still more frequently, such masses of decayed galena, 
and the contiguous veinstones, are studded over with crys- 
VOL. IV. L I 
