[ 193 ] 



XXXIII, On Gems. By W. H. Pepys./«;?. Esq. P. R. L 

 Member of the Askesian Society. Read in the Session 

 1S02-3*. 



JL HIS class of bcxlies has engaged the attention of all ranks 

 of society from the earliest agcs : their beauty, and property 

 of decomposing light, producing the variegated colours of 

 the prism and the rainbow, will always procure them a place 

 in the most splendid and sumptuous displays of human 

 magnificence. 



To the philosopher they open a wide and extended field 

 in his inquiries into the secret works of nature ; and the 

 cabinet of the mineraloijrist becomes more interesting and 

 enlivened by their presence. 



We find the greater part of them were used in the costume 

 of the priests of the temple : — " And they set in it (the breast- 

 plate of the priest) four rows of stones : the first was a 

 sardius, a topaz, and a carbuncle, — this was the first row; 

 and the second row an emerald, a sapphire, and a diamond; 

 and the third row a ligurc, an agate, and an amethyst ; and 

 the fourth row a beryl, an onyx, and a jasper ; and they 

 were inclosed in ouches (or foils) of gold in their in- 

 closings." 



Those which are most esteemed, and reckoned the most 

 valuable, with the moderns, are : 



1. The diamond. 6. The hyacinth. 



2. The ruby. 7. The beryl. 



3. The sapphire. 8. The amethyst. 



4. The emerald. 9. The garnet. 



5. The topaz. 10. The chrysolite. 



1. The diamond, formerly classed with the siliceous ge- 

 nus, is now acknowledged to belong to the inflammable or 

 carbonaceous : it has the greatest degree of transparency, 

 and is the most beautiful and most brilliant of all the pre- 

 cious stones. It produces only single refraction, but its 

 refractive powers are stronger than that of any other body; 

 it separates the colours better; and this is the cause why it 

 sparkles with so much lustre, especially in the light of the 

 sun. An artificial gem of glass does not reflect the light 

 from its hinder surface until that surface is inclined in an 

 angle of 41 degrees, while the property of the diamond is 

 such as to occasion all the light to be reflected, which fulls 



* Copied, by permission, from the Records pf the Society. 



VoLTXV'II.No.tiz. N on 



Decenibcr 1&03. 



