ORES OF THE CHAMPLAIN, TACONIC AND METAMORPHIC ROCKS. 
505 
The lead ore^f this mine contains a small quantity of silver. I believe I was the first to 
detect it, in the winter of 1837. I did not ascertain the proportion of silver, but think it 
probable that it may be worth separating by the improved methods of concentrating the silver 
in smaller portions of the lead, and thus increasing the richness in a small proportion of the 
lead obtained from the ore.* Prof. Beck repeated my process of cupellation, and also 
obtained silver. 
As this method of cupellation is very easy to be performed by any person who can use a 
blowpipe, is very neat, and can be effected in a few minutes, it is detailed below. It can be 
performed at any time by apparatus that will not necessarily occupy more space in a person’s 
pocket than a pocket knife, and saves the expense and trouble of a cupelling furnace, muffles, 
etc., which must necessarily be fixtures, and not easily portable. 
If the ore to be examined for silver or gold, be a lead ore, it is to be reduced to the metallic 
state by the ordinary methods. A small piece of the lead, of the size of a duck shot or 
larger, is to be placed on a thin slip of mica, and then melted by the blowpipe flame of a 
candle or lamp. As the heat increases above the melting temperature of the lead, the 
globule will become perfectly brilliant; and finally a peculiar flickering, brilliant surface will 
show itself, caused by the oxidation of the metal and the fusion of the oxide of lead. The 
oxide of lead melts at the temperature at which this appearance is developed, and spreads 
itself on the mica. It soon ceases to spread, and collects around the globule of melted lead, 
which is continually diminishing in magnitude, in consequence of the oxidation of the metal 
in the oxidizing blowpipe flame. When the globule of melted lead is nearly buried in the 
mass of the surrounding oxide, the slip of mica should be permitted to cool. The globule 
of lead should then be removed by forceps, or other means, to another place on the slip of 
mica, where the same oxidizing process is to be repeated successively. Finally, when the 
globule shall have been reduced to the size of a small grain of sand, it should be placed on a 
fresh, clean slip of mica, and again heated in the same manner. If the lead contains the 
least trace of silver, it is easily made manifest in this way, because, the silver, when once 
free of lead, (which continues tq oxidize to the last,) remains unchanged, as a brilliant white 
globule, which can be frequently seen distinctly with the naked eye, and when too small for 
this, by examination with the magnifier. If the oxidation of one globule of the lead does not 
give decisive indications of silver, a satisfactory conclusion as to the lead being argentiferous 
or not, may be obtained by oxidizing five to ten such globules down to a very small size, and 
then uniting these by fusion on a slip of mica, and continuing the oxidation to its ultimate 
limit. A person accustomed to blowpipe manipulation can determine in a few minutes if 
silver be present in any lead which may be suspected to contain it. With the table blowpipe. 
• “ A detailed account cf this process, with various statements, intended to show its importance to Great Britain, is contained 
in the abstract of the proceedings of the last meeting of the British Association for the Advancement of Scienee, published in 
the London Atheneum. It has been republished in the Family Magazine, and perhaps in other American periodicals.” (Third 
Annual Geological Report of New-York, 1839, p. 51.) 
Geol. 1st Dist. 
64 
