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POPULAR SCIENCE REVIEW. 
horses belonging to Maha Eaja, one of the eastern princes, were 
estimated to have been worth an immense sum, besides which, 
on grand occasions, they were adorned with the finest jewels of 
the treasury, including the celebrated diamond the Koh-i-noor, 
or Mountain of Light. Among the Mohammedans, the corne- 
lian is regarded as possessing many virtues, and is still further 
esteemed, from a saying attributed to Mohammed, that ^‘he 
who seals with a cornelian, will always be in a state of blessed- 
ness and joy.” 
More than two hundred years ago, the Grermans selected 
twelve stones as typical of the twelve months of the year, each 
stone bearing an engraved sign of the month. These stones 
were very fashionable, and many persons of both sexes wore, 
mounted in rings, the stone of the month in which they were 
born.* Thus : — January = Grarnet; February = Amethyst ; 
March = Bloodstone ; April = Sapphire ; May = Emerald ; June 
= Onyx; July = Cornelian ; August = Sardonyx ; September 
= Chrysolite ; October = Aquamarine ; November = Topaz ; 
December = Turquoise or Malachite. 
The four rings sent by Pope Innocent III. to King John, 
contained each a different coloured stone, as emblematical of 
the cardinal virtues, faith, hope, charity, and good works, which 
were respectively represented by the emerald, sapphire, garnet, 
and topaz. 
The fine stones, or gems proper, are generally transparent, 
and either colourless, red, blue, green, yellow, violet, or have 
a chatoyant lustre. They are amongst the hardest of mineral 
substances, either equal to, but mostly harder than rock-crystal ; 
hence to some extent their value, and for this reason they are 
employed for the pivots of watches, and other instruments of 
precision. Another physical character connected -with them is 
their comparative coldness to the touch, a test sometimes used 
to distinguish them from false' or imitative gems ; even quartz 
possesses to some extent this quality — a fact apparently known 
to the people of ancient Kome, who are said to have used balls 
of rock-crystal (such as those seen in the British Museum from 
Japan), for cooling their hands in the summer season. Similar 
small globes of rock-crystal have also been used as divining 
stones. 
The crystalline forms which the gems or stones assume vary 
greatly, and may sometimes be used as a distinguishing cha- 
racter. The diamond, spinel, and garnet present various 
modifications of the cubical system ; the sapphire, beryl, emerald, 
as well as quartz and tourmaline, belong to the hexagonal system ; 
the topaz and chrysolite crystallise in rhombic, and the zircon 
* Jackson : Minerals and their Uses j ” Emanuel on Precious Stones. 
