584 BOOK XII. 



boiled in the pots, cannot be made hard. The mixtures containing bitumen 

 are also treated in the same manner as those containing sulphur, in pots 

 having a hole in the bottom, and it is rare that such bitumen is not highly 

 esteemed. 



Since all sohdified juices and earths, if abundantly and copiously mixed 

 with the water, are deposited in the beds of springs, streams or rivers, and the 

 stones therein are coated by them, they do not require the heat of the sun or 

 fire to harden them. This having been pondered over by wise men, they dis- 

 covered methods by which the remainder of these solidified juices and unusual 

 earths can be collected. Such waters, whether flowing from springs or 

 tunnels, are collected in many wooden tubs or tanks arranged in consecutive 

 order, and deposit in them such juices or earths ; these being scraped off 

 every year, are collected, as chrysocolla^^ in the Carpathians and as ochre in 

 the Harz. 



There remains glass, the preparation of which belongs here, for the 

 reason that it is obtained by the power of fire and subtle art from certain 

 sohdified juices and from coarse or fine sand. It is transparent, as are certain 

 sohdified juices, gems, and stones ; and can be melted like fusible stones and 

 metals. First I must speak of the materials from which glass is made ; 

 then of the furnaces in which it is melted ; then of the methods by which it 

 is produced. 



It is made from fusible stones and from solidified juices, or from other 

 juicy substances which are connected by a natural relationship. Stones 

 which are fusible, if they are white and translucent, are more excellent than 



illuminant is Strabo's quotation (xvi., i, 15) from Posidonius : " Asphaltus is found in 

 " great abundance in Babylonia. Eratosthenes describes it as follows : — The liquid asphaltus, 

 " which is called naphtha, is found in Susa ; the dry kind, which can be made soHd, in 

 " Babylonia. There is a spring of it near the Euphrates. . . . Others say that the liquid 

 " kind is also found in Babylonia. . . . The liquid kind, called naphtha, is of a singular 

 " nature. When it is brought near the fire, the fire catches it. . . . Posidonius says 

 " that there are springs of naphtha in Babylonia, some of which produce white, others black 

 " naphtha ; the first of these, I mean white naphtha, which attracts flame, is liquid sulphur ; 

 " the second or black naphtha is hquid asphaltus, and is burnt in lamps instead of oil." 

 (Hamilton's Translation, Vol. in., p. 151). Eratosthenes lived about 200 B.C., and Posidonius 

 about 100 years later. Dioscorides (i., 83), after discussing the usual sources of bitumen 

 says : " It is found in a liquid state in Agrigentum in Sicily, flowing on streams ; they use it 

 " for hghts in lanterns in place of oil. Those who call the Sicilian kind oil are under a delusion, 

 " for it is agreed that it is a kind of liquid bitumen." Pliny adds nothing much new to the 

 above quotations, except in regard to these same springs (xxxv., 51) that " The inhabitants 

 " collect it on the panicles of reeds, to which it quickly adheres and they use it for burning 

 " in lamps instead of oil." Agricola (De Natura Fossilium, Book iv.) classifies petroleum, 

 coal, jet, and obsidian, camphor, and amber as varieties of bitumen, and devotes much space 

 to the refutation of the claims that the last two are of vegetable origin. 



**Agricola (De Natura Fossilium, p. 215) in discussing substances which originate from 

 copper, gives among them green chrysocolla (as distinguished from borax, etc., see Note 8 

 above), and says : " Native chrysocolla originates in veins and veinlets, and is found mostly 

 " by itself like sand, or adhering to metallic substances, and when scraped off from this 

 " appears similar to its own sand. Occasionally it is so thin that very little can be scraped 

 " off. Or else it occurs in waters which, as I have said, wash these minerals, and afterward 

 " it settles as a powder. At Neusohl in the Carpathians, green water flowing from an 

 " ancient tunnel wears away this chrysocolla with it. The water is collected in thirty large 

 "reservoirs, where it deposits the chrysocolla as a sediment, which they collect every 

 " year and sell," — as a pigment. This description of its occurrence would apply equally 

 well to modern chrysocolla or to malachite. The solution from copper ores would deposit 

 some sort of green incrustation, of carbonates mostly. 



