On Cupellation with the Blowpipe. 413 
meastired with considerable accuracy by means of a micrometer 
microscope. ‘This degree of accuracy is sufficient for all practical 
purposes, for if ten grains of lead only gave ;,534,575 grain of sil- 
ver, 3124 tons would be required to produce one oz. of silver. 
If ten grains of lead or rather alloy cupelled yield ;,';; grain of 
silver or ;53;55 Of its weight, it would contain only 31 oz. per 
ton, or if it yielded ;1, grain, it would be 32 ounces of silver per 
ton of lead or alloy. 
Means of estimation like those mentioned are sufficiently accu- 
tate for practical purposes, by using one grain weight of the alloy 
or one mixed with a suitable quantity of lead. 
Quantities of silver far more minute can be detected by suita- 
ble care in blowpipe cupellation. With a good microscope a 
globule of silver ;~,; inch diameter ought to be visible, which 
would weigh about +5.553.bs5.c07 Of a grain.* A metal that 
about one-sixth in those from ;', to ;4;, about one-seventh in 
The weights of spheres of gold or silver of any other diameters 
than those in the table, are easily calculated by the formula W= 
CDs. is a constant for the same metal, and represents the 
Weight of a sphere of the metal one inch in diameter. This weight 
ee ese ee Fe i 
._” For 1 cubic inch of distilled water weighs 252 46 grains. If the specific grav- 
ity of silver be called 10-5, then 1 cubic inch of silver would weigh rains 
0:5 the sp. gr. of silver = 2640:8 grains. Solids are proportional to the cubes 
of their like linear dimensions. An angle of 1’, the limit of the visual angle, at 
@ distance of 8 inches subtends soo von Of an inch, = inch. ».(linch) 
— 
* (ssta0)*® : : 26408 grains : t= y55z8 Se0-000-000. = STISTETOTS 
about one six thousandth Shee of a an or in a spheroid form, a globule of 
about one ten thousand millionth of a grain. Sinall globules may be rendered 
more distinct by pressure in an agate mortar, which not only gives them a greater 
area, but a much greater reflecting surface. ; 
