THE GRAND DUKE'S DIAMOND 347
be
183-2/3 carats nearly. The conclusions to be drawn, therefore, are,
that, in the first place, the stone has not had any additional facets
cut upon it, and that it is, in fact, in the same con-• dition as when
Tavernier gave its weight at 139-1/2 carats ; the difference between
that weight and the 139-1/5 Florentine carats is so small, amounting to
only 3/10-ths of a carat, that it may be fairly attributed to
difference in the accuracy of the methods of weighment employed by
Tavernier and Schrauf respectively.
Hence
we may fairly conclude that in this instance, at least, the carat used
by Tavernier was the ' Florentine ' ; and that being so, it is hardly
conceivable that, when mentioning Indian stones on the very same pages
as those where he describes the Grand Duke of Tuscany's diamond, he had
other carats in view. Consequently, with greater confidence than I
could venture to assume when the Appendix of vol. i. was written, I now
suggest the hypothesis that Tavernier's carats were the light
Florentine carats, which are exactly 4 per cent, lighter than modern
English carats. Thus the English carat of -2054 grm. less 4 per cent.
(-0082) = -1972 grm. which is the precise value of the Florentine carat.
The
conclusion thus arrived at as to the carat of Tavernier having been the
light Florentine, involves a reduction in the value of the rati, which
has been calculated in the earlier part of his work on the supposition
that it was equal to £ths of the modern French and English carat. It
must therefore be reduced by 4 per cent, likewise, so that instead of
2-77 troy gr., it must stand at 2-66 troy gr. This value, it should be
added, is identical with that derived from Tavernier's own statement,
that 6 melscals or 181-1/3 ratis = 1 French ounce (i. e. 482-312 gr.
troy), since 482-312 / 1811 = 2-66. I am accordingly compelled to
accept this value finally as being that of Tavernier's pearl rati ; and
I must ask readers to accept this conclusion, which was given as an
alternative to 2-77, in the Appendix to vol. i,1 instead of the latter, which was adopted in the text.
In
the following table the weights in carats of the principal stones
mentioned by Tavernier are enumerated, and in the last column these
weights, reduced by 4 per cent., show the equivalent values in English
carats.
4. On the weights of some of the Diamonds, other Precious Stones, and Pearls, mentioned and figured by Tavernier.
Assuming that our argument is well founded as to the carats mentioned in the text having been Florentine carats,
1 See vol. i. 332 ff.
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