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A Text-Book of Precious Stones for Jewelers and th

The old carat was approximately


DECIMAL SYSTEM OF SUBDIVISION OF THE CARAT. With the adoption of the metric carat the custom of expressing parts of a carat in common fractions whose denominators were powers of the number 2 (1/2, 1/4, 1/8, 1/16, 1/32, 1/64) was discarded as awkward and slow for computation and the decimal system of subdivision was adopted. Thus the metric carat is divided into tenths and one hundredths. It is customary, however, to sum up the one hundredths and express them as the total number of one hundredths and not to express them as tenths. Thus, a stone of 2.57 carats is said to weigh "two and fifty-seven hundredths carats." The decimal system of subdivision of the carat makes the figuring of values simpler where no tables are handy. Of course, new tables were at once prepared when the new carat was adopted and they afford a rapid means of ascertaining the value of a stone of any weight when the price per carat is known. Should it become necessary to convert the weight of a stone from its expression in the old system to that of the new, one need only get 1.02-1/2% of the old weight. (The old carat was approximately .205 g., while the new one is .200 g. Hence one old carat

.205 .102-1/2 is ---- = -------- = 102-1/2% of a new one.) .200 .100

METHOD OF CONVERTING WEIGHTS. If the old weight has fractions these should first be changed to decimals for convenience. For example, suppose it is wished to

change 2-1/4 1/16 old carats to metric carats. 1/4 = .25 and 1/16 = .0625. Hence 2-1/4 1/16 = 2.3125. Now get 102-1/2% of this: (2.3125 x 1.025 = 2.37 metric carats).

If, for any reason one should need to change from metric carats to old U. S. carats one should multiply by .9756

( .200 g. ) ( ------- = .9756 ) ( .205 g. )

As was said in Lesson XXV., pearls are sold by the _pearl grain_, which is arbitrarily fixed at 1/4 of a carat. With the change to the metric carat the pearl grain was correspondingly changed and its weight is now 1/4 of .200 g. = .05 g., as expressed in the metric system.



Since it is necessary for a nation, as well as for an individual, to have an income, and since articles of luxury are more easily taxed than are those of necessity, the traffic in gems and their imitations has frequently been made a source of revenue to our government. Usually the per cent. charged as tariff has been comparatively low, especially upon very valuable gems, such as diamonds and pearls, for the reason that too high a tariff would tend to tempt unscrupulous dealers to smuggle such goods into the country without declaring them. When the margin of difference between the values, with and without the tariff, is kept small the temptation is but slight, when the danger of detection and the drastic nature of the usual punishment are taken into account. Rough stones have frequently been allowed to enter the country duty free because they were regarded as desirable raw materials which would afford employment to home industry.

The tariff laws of October 3, 1913, made, however, some sweeping changes in the policy of our government toward precious stones and as those laws are still in force (April 4, 1917) this lesson will attempt to set forth clearly the exact conditions under the present law.

Perhaps the paragraph of first importance to the trade is No. 357 which reads as follows.

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