Chap. 54.] ACHATES. 439 



of Berenice. It is partly composed of crystal, and hence it is 

 that some have called it ** root of crystal." It takes its name 

 *'iris" from the properties which it possesses; for, when 

 struck by the rays of the sun in a covered spot, it projects upon 

 the nearest walls the form and diversified colours of the rain- 

 bow ; continually changing its tints, and exciting admiration 

 by the great variety of colours which it presents. That it is 

 hexahedral in form, like crystal, is generally agreed ; but some 

 say that it is roughen the sides and of unequal angles; 

 and that, when exposed to a full sun, it disperses the rays 

 that are thrown upon it, while at the same time, by throw- 

 ing out a certain brightness'^ before it, it illumines all ob- 

 jects that may happen to be adjacent. The stone, however, 

 as already stated, only presents these colours when under 

 cover ; not as though they were in tlie body of the stone 

 itself, but, to all appearance, as if they were the result of the 

 reflected light upon the surface of the wall. The best kind is 

 the one that produces the largest arcs, with the closest resem- 

 blance to the rainbow. 



" Iritis " is the name of another stone, similar to the last in 

 all other respects, but remarkable for its extreme hardness. 

 Horus says, in his writings, that this stone, calcined and tritu- 

 rated, is a remedy for the bite of the ichneumon, and that it is 

 a native of Persia. 



CHAP. 53. LEK08. 



The stone called *'leros"'^ is similar in appearance, but does 

 not produce the same effects. It is a crystal, with streaks of 

 white and black running across it. 



CHAP. 54. ACHATES ; THE SEVERAL VABIET1E8 OF IT. ACOPOS ; 



THE EEMEDIES DERIVED FROM IT. ALABASTRITIS ; THE RE- 

 MEDIES DERIVED FROM IT. ALECTORIA. ANDEODAMAS. AR- 

 GTRODAMAS. ANTIPATHES. ARABICA. AROMATITIS. ASBESTOS. 

 ASPISATIS. ATIZOE. AUGETIS. AMPHIDANE8 OR CHRYSOCOLLA. 

 APHRODISTACA. AP8YCT0S. -EGYPTILLA. 



Having now described the principal precious stones, classified 



quartz iridized internally, or prismatic crystals of Limpid quartz, which 

 decompose the rays of the sun. 



*^ The reading and meaning of this passage are very doubtful. 



" The reading is doubtful, " zeros " and " erros " being given by some 

 MSS. Ajasson hazards a conjecture that it may have been a variety of 

 quartz, formed of a concretion of agates united by a cement of a similar 

 nature. 



