396 pltnt's NATURAI* HISTOET. [Book XXXVII. 



us, is the one that was consecrated by Julia Augusta in the Ca- 

 pitol, and which weighed about one hundred and fifty pounds.* 

 Xenocrates speaks of having seen a vase of crystal, which held 

 one amphora,'^ and we find other writers mentioning a vessel 

 from India which held four sextarii. For my own part, I can 

 positively say, that there is crystal amid the crags of the Alps, 

 so difficidt of access, that it is usually found necessary to be 

 suspended by ropes in order to extract it. Persons who are 

 experienced in the matter detect its presence by certain signs 

 and indications. ^ 



Crystal is subject to numerous defects, sometimes present- 

 ing a rough, solder- like, substance, or else clouded by spots 

 upon it; while occasionally it contains some hidden hu- 

 mour^ within, or is traversed by hard and brittle knurrs,®^ 

 which are known as " salt grains."^^ Some crystal, too, has a 

 red rust upon it, while, in other instances, it contains fila- 

 ments that look like flaws, a defect which artists conceal by 

 engraving it. But where crystals are entirely free from de- 

 fect, they are preferred uncut ; in which case, they are known 

 as " acenteta,'*®^ and have the colour, not of foam, but of 

 limpid water. In the last place, the weight of crystals is a 

 point which is taken into consideration. 



I find it stated by medical men that the very best cautery 

 for the human body is a ball of crystal acted upon by the rays 

 of the sun."* This substance, too, has been made the object of 

 a mania ; for, not many years ago, a mistress of a family, 

 who was by no means very rich, gave one hundred and fifty 

 thousand sesterces for a single basin made of crystal. 'Nero, 

 on receiving tidings that all was lost, in the excess of his 

 fury, dashed two cups of crystal to pieces ; this being his last 

 act of vengeance upon his fellow-creatures, preventing any 

 one from ever drinking again from these vessels. Crystal, 

 when broken, cannot by any possibility be mended. Vessels in 



•8 Ajasson remarks that blocks have been found in Switzerland, weigh- 

 ing above eight hundred pounds. 



59 Forty-eight sextarii. See Introduction to Vol. III. 



60 This " vomica," Ajasson says, is either water, azote, rarified oxygen, 

 or water in combination wit)i naphtha. 



61 " Centra," knots, or flaws. See B. xvi. c. 76, where he speaks of 

 the "centra" in marble. See also Beckmann, Hist. Inv. Vol. I. p. 471. 

 John's Edition. 6* " Sale." See Note 46 above. 



63 "Without flaw." 6i gee B. xsxvi. c. 67. 



