1808. ] 
which is. called the ‘* Remedy for the 
Matter of the Mint :**. according to this 
if the deficiency of the coin, in the ag- 
gregate, is lefs than the fixch part of a 
carat, equal to 40 grains of fine gold, 
in the pound of ftandard, or the -4,d part 
of the value, the ager is held excula- 
bie. ' 
Not only is the equal diftribution of 
the two metals, fuch as gold and filver, 
difficult to be made ; but if they are kept 
in fufion under certain circumftances, a 
feparation, more or lels perfe& fome- 
times takes place; this feparation appears 
to be according to the relative affinities 
and f{pecific gravities of the two metals, 
Proceedings of Learned Societies. 
‘machine in which they were placed, 
451 
and is the fooneft effe&ed when the metals 
have not been perfeétly mixed. 
Long-continued friction, produces alfo 
a diminution in the fpecific gravity of 
metals. Thus, when three pieces of gold 
were oppofed to three other pieces of fi- 
mular quality, and made to rub againf 
each other for a confiderable time, or till 
there had been 200300 revolutions of the 
the 
{fpecific gravity of the pieces was dimi- 
nifhed from 19.277 to 19,171. In other 
caies the diminution varied according. to 
the nature of the alloy, as will be feen in 
the following tabie: 
Quality. 
» 'Gold of:'23 car. 3d, fine 
Gold alloyed with filver 
copper - 
I 
2 
3° 
4. 
by 
6 
ya 
—— 
When twelve pieces of copper were 
made to rub again(t each other, after 
22200 revolutions, a very apparent dimi- 
nution was found to be the refult ; for 
the {pecific gravity was, 
Before friction After friétion 
3.735 8.233 
Rolling and annealing preduce alfo an 
alteration in the fpecific gravity of gold ; 
by the former procels, the {pecific gra- 
vity is increafed, by the latter it is dimi- 
nifhed. As therefore the fpecific.gravity 
of metals is liable to be influenced by 
fuch a variety of caules, it is almoft in 
vain to expect abfolute precifion, and con- 
fequently it will be improper to form opi- 
ions upon {mall fra€tional variations. 
From many experiments made with every 
poffible piecaution, the foliowing retults 
are elteemed as accurate. 
Geld made itandard by filver 17.927 
by filver and 
copper a - o 976944 
by copper 17.157 
Now, as our gold coin commonly con- 
trins filer as part of the alloy, and as at 
different times this proportion of fiver 
muft have been various, particularly when 
the gold of Portugal, which is already al- 
Joyed with Gilver, was brought to the mint, 
it naturally follows that, exclulive of the 
Monrary Mac. No. 108. 
re emer t enn Pra re 
filverand copper 
copper and iron 
copper and tin - 
Gold and copper in equal parts - 
Spe. Gra.| Spe. Gra, 
before friét.| atter frict. 
- - 19.277 19.171 
attic 18 092 18.055 
- 13.184 18.302 
ate 18.053 18 014 
- jy de 17-095 
- 17.607 17.581 
- 12.142 12.139 | 
| 
many other caufes of variation, the fpeci- 
fic gravity of our flandard gold muft oc- 
cafionally be different, according to the 
relative proportions of filver and copper 
which compofe the alloy ; hence the diffe- 
rence of the {pecific gravity which various 
authors have found belonging to the gold 
coin of this country. In another table 
Mr. Hatchett hes given the fpecific ora- 
vity of fome Engl. th-gold coins from a 
five-cuinea-piece which was made in the 
reign 1 of Charles II. to the feven-fhilling- 
pieces of 1802 ; and though he thinks that 
the {maller the coin, the greater the {peci« 
fic gravity, vet he gives the average f{pe- 
cific gravity of our gold coin, at the pre- 
fent time, at 17.724. (To be Concluded 
in our next.) 
The Royal Society commenced its fit. 
tings November 10, for the feafon, when 
the firft part of the Croonian lecture on 
mufcular motion was read. 
The Antiquarian Society commenced 
their meetings on the fame evening. The 
death of the treafurer, Mr. Topham, was 
announced trom the chair, and it is under- 
itood that Mr. Bray will be candidate for 
the vacant treafvrefhip. Some interetting 
papers on antiquities were read by the 
fecretary. 
3 N NEW 
