502 plijtt's natubal history. [Book XXXI. 



manner, too, it has be(?n found in the thirsting deserts of 

 Africa, as far as the oracle of Hammon,^^ a locality in which 

 the salt increases at night with the increase of the moon. 



The districts of Cyrenaica are ennobled, too, by the production 

 of hammoniacum,''^ a salt so called from the fact of its being 

 found beneath the sands ^ there. It is similar in colour to the 

 alum known as *' schiston,"^ and consists of long pieces, by no 

 means transparent, and of an unpleasant flavour, but highly 

 useful in medicine ; that being held in the highest esteem, 

 which is the clearest and divides into straight^ flakes. There 

 is one remarkable fact mentioned in connexion with it: so long 

 as it lies under ground in its bed^ it is extremely light, but the 

 moment it is exposed to the light, it is hardly credible to what 

 an extent its weight is increased. The reason for this is evi- 

 dent :^ the humid vapours of the excavations bear the masses 

 upwards, as water does, and so aid the workmen. It is adulte- 

 rated with the Sicilian salt which we have mentioned as being 

 found in Lake Cocanicus, as also with that of Cyprus, which 

 is marvellously like it. At Egelasta,*' in Nearer Spain, there 

 is a salt, hewn from the bed in almost transparent blocks, and 

 to which, for this long time past most medical men, it is said, 

 have given the preference over all other salt. Every spot in 



^^ More commonly known as Jupiter Ilaramon. 



^^ See B. xii. c. 49, and B. xxiv. c. 28, for an account of gum resin am- 

 moniac, a produce of the same locality. The substance here spoken of is 

 considered by Beckmann to be nothing but common salt in an impure state. 

 See his Hist. Inv. Vol. II. pp. 398-9, where this passage is discussed at 

 considerable length. Ajiisson, on the other hand, considers it to be Hydro- 

 chlorate of ammonia, the Sal ammoniac of commerce. According to some 

 accounts, it was originally made in the vicinity of the Temple of Jupiter 

 Ilammon, by burning camels' dung. 



* Called afijjioQ, in Greek. " See B. xxxv. c. 52. 



2 Sal ammoniac crystallizes in octahedrons. 



■* " Intra specus suos." On this passage, Beckmann says, " From what 

 is said by Pliny it may with certainty "be concluded that this salt was dug 



up from pits or mines in Africa. Many kinds of rock-salt, taken from 



the mines of Wieliczka, experience the same change in the air ; so that 

 blocks which a labourer can easily carry in the mine, can scarcely be lifted 

 by him after being for some time exposed to the air. The cause here is 

 undoubtedly the same as tliat which makes many kinds of artificial salt to 

 become moist and to acquire more weight." — Vol. II. p. 399, Bohri's Ed. 



'^ According to modern notions, his reason is anything but evident. 



■^ In Celtil)eria. lie alludes to the mountain of salt at Cardona, near 

 ]Montserrat in Catalonia. 



