Value of Native Gold, &c. 205 
a delicate apparatus which I have used on several occa- 
sions for the purpose of ascertaining the specific gravities 
of bodies. A careful comparison was first made of the 
various weights employed, and an experiment of the amount 
of accuracy with which the specific gravity of a known 
material could be determined gave me every reason to be 
satisfied with the character and condition of the balance: 
The following detail will enable the Society to judge how 
far this confidence was well founded. ‘The standard value 
of Gold is £3 17s. 103d. per ounce, and according to this 
a sovereign should weigh 123°27 grains, and its specific 
gravity should be, as before stated, 17589. 
Every day’s circulation, however, must diminish the 
weight of a sovereign, though it does not affect its specific 
gravity. A sovereign, not of a very old date, being placed 
in the scale, its weight was found to be 123°12 grains, 
showing a loss of ‘15 of a grain, while its specific gravity 
appeared to be 17588, a difference from the standard specific 
gravity of too trifling an amount to merit notice. Having 
thus shown that confidence might be placed in the instru- 
ments employed, I will explain the mode in which the 
experiments were conducted. 
The specimens. were first weighed very carefully, the 
balance being delicate enough to turn with avery small 
fraction of a grain when loaded with upwards of 2 ounces. 
The smallest weight employed was the 1's ofa grain. The 
weight being noted, the specimen was then suspended by a 
fine hair to a hook on the underside of the scale in a glass 
of distilled water, care being taken to free it from any 
bubbles of air which might perhaps exist in cavities on the 
metal, or adhere to its surface. Allowance was made for the 
hair used in suspending the specimen, and the weight with 
the necessary deductions was recorded. The difference 
s 3 
