FROM NAZARETH TO TIBERIAS, 
273 
$uch ao appearance, therefore, in the approach to the Lake of 
Tiberias, is only a parallel to similar phenomena exhibited by 
rocks near the lakes of Locarno and Bolsenna in Italy; by 
those of the Wenner lake in Sweden ; by the bed of the Rhine, 
near Cologne in Germany ;* by the valley of Xlonca. in the 
territory of Verona,f the giant’s causeway of th t pont du Bri ■* 
don , in the state of Venice,! and numerous other examples in 
the same country; not to enumerate instances which occur over 
all die islands between the north coast of Ireland and Iceland, 
as well as in Spain, Portugal, Arabia, and India.5 When these 
crystals have attained a regularity of structure, the form is often 
hexagonal, like that of cannon spar, or the Asiatic and Ameri¬ 
can emera]d.J It is worthy of remark, that Patrin, during his 
visit to the mountain Odon Tchelon , in the deserts of oriental 
Tartary, discovered, in breaking the former kind of emerald 
when fresh taken from the stratum wherein it. lies,not only 
the same alternate convex and concave fractures which cha¬ 
racterize the horizontal fissures of certain hasaltie pillars,ff but 
-'** The town gates of Cologne are constructed of stones having the formdeommoniy 
called basaltic ; and similar substances may be observed in the walls. 
f See the account published by the Abate Fort is, Bella Valle di Rdnca be! ter- 
ritorio Veronese,’^printed at Venice in 1778. 
X &ee “■ Memoria de’ Monto Colonnari di S: E. il Signer Chvaliere Giovanni 
Strange,” printed at Milan, in 17.78, for a beautiful representation of this causeway; 
engraved by Fes sard, from a drawing by Be Vtyrenc. Also the representations given 
in the LX 1st volume of the philosophical transactions of the rtjyal society of Lon¬ 
don, tab. 19, p. 383. Ac. 
ySee the numerous other instances mentioned by Jasiesdn, (Syst. of Mia. vol. i, 
p. 372. Edin. 1801.) in sitting 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 phenomena of crystallization upon a 
large scale, whenever the prisms are large enough to: be considered as columns. 
Ii Commonly called Siberian Beryl and Peruvian Emerald. Hauy, Patrin, and others, 
have shown the impropriety of separating these varieties, o.f the emerald. Some con¬ 
sider the colouring principle as sufficient to distinguish them, which is the oxide of 
iron in the Asiatic emerald, and that of chromium in the American. But it should be 
observed, that the emerald of Peru does not always, contain chromium: neither is it 
yet known that it does not contain iron. The author b‘asspecimens of the Peruvian 
emerald,, white and limpid as the purest'rock crystal. What thfen becomes of a dis¬ 
tinction founded upon colour? Patrin preserves the names of emerald chrysolite, and 
aigue marine as applicable to the Siberian mineral; but lie says, ” Ces gemmes ont la 
meme forme cristaliine, la meme pesantcur specitique, la meme dprete que Feme- 
ramie du Perou: elles contiennent la meme quantity de'glucine; elie? ont encore ia 
double refraction deTemeraude. Elies n’en different, dont" que par la couleur; et 
Ton a vu par l’exemple du rubis d’Orient combien la couleur; est nulie aux yeux du 
naturalist.e.” Hist. Nat. des Min. tom. ii, p. 23. Paris, An- .9. 
Je iis une remarque a, cdtte occasion; c T est'que ces gemmesi.qui deviennent s;i 
dures, etoient singuiierement lriabies au sortir.de leurs g.ites: plusieurs gros prismes- 
se briserent entre mes mains.” (Hist. Nat., des Min. tom. ii. p. 32.) It is the same 
with the common flint, which,-when first taken from a bed of chalk, sometimes breaks 
in the hand, and is penetrated with visible moisture. This is also the case with re¬ 
gard to the Hungarian opals; the workmen often expose them to the sun., before they 
venture to remove them. 
tf ‘ II off re un accident remarquable, et que j’ai observe le premier dans ces gemmes 
e’est que ces extremites, au lieu d’etre planes, ont une saillie arrondie comme le 
basalts articles. Cet. accident se rencontre egalment dans les emerauds et ies aigues* 
marines de la meme montagne J’en ai des exemplaires de toutes les nuances, qui of- 
iyeul css articulations, soil eu relief, so'it e'a creux,” Hist, Nat. des Min. tom., ii- 
