NAZARETH TO TIBERIAS. 193 
coaiBt of Ireland and Iceland, as well as in chap. 
Spain, Portugal, Arabia, and India*. When tliese ' , — ' 
crystals have obtained a regularity of structure, 
the form is often hexagonal, like that of Cannon 
Spar, or of the Asiatic and American emerald''. 
It is worthy of remark, that Pairin, during his 
visit to the mountain Odon Tchelon, in the deserts 
of Oriental Tahtary, discovered, in breaking the 
former kind of emerald, when fresh taken from 
(4) See the numerous other instances mentioned by Professor 
Jameson, {Syst.'of Min. vol.1, p. 272. Edin. 1804.) in stating the 
geographical situation of basalt ; a vague term, as he properly expresses 
it, which ought to be banished from mineralogy : it is in fact applied 
to any substance which exhibits the phEcnomena of crystallization upon 
a large scale, whenever the prisms are large enough to be considered 
as columns. 
(5) Commonly called Siberian Beryl, and Peruvian Emerald, H auy, 
Patrin, and others, have shewn the impropriety of separating these 
varieties of tTbe emerald. Some consider the colouring principle as suf- 
ficient to distinguish them, which is oxide of iron in the /Jsiutic emerald, 
and of chromium in the American. But it should be observed, that the 
emerald of Peini does not always contain chromium; neither is it yet 
known that it docs not contain iron. The author has gpecimens of 
the Peruvian emerald, white and limpid as the purest rock crystal. 
What then becomes of a distinction founded upon colour ? Patrth 
preserves the names of emerald, chrysolite, and ai^tte marine, as all 
applicable to the Siberian mineral; but he says " Ces gemmes ont la 
mime forme crisialline, la mime pisanteur spicifique, la meme duret6 
que l'4meraude du Perou; elks contienneni la mime quantiti de glucine; 
elles ont encore la double refraction de I'imeiaude. Elles n'en diffirent 
done que par la coulcur ; et Von a vu, par I'eremple du rubis d" Orietit, 
eombien la couleur est nulle aux yeux dunaturaliste." Hist, Nat. des 
Min. torn. II. p. 23. Paris^ An 9. 
