122 Notes on Foreign Geology and Mineralogy. 
perature of 75° Centigrade. At the Olanesti springs there exists a 
medical establishment. 
The following is the description given by M. Pierre Poenar (Loe. 
cit.) of the Salt Lake Balta-Alba, at the end of his account of the 
mineral riches of Roumania. ‘This lake is situated at 12 kilometres 
(about 74 miles) from the town of Rimnik-Sarat, in the middle of a 
vast plain; it is 7 kilométres (about 44 miles) long, and varies in 
breadth from two to three hundred metres; its depth is from one to 
two métres only. The water of this lake is very salt, and forms 
saline deposits on the borders, where it is of a reddish-brown colour, 
and nauseous to the taste, on account of the multitudes of its aquatic 
birds, whose excrement (guano) is constantly driven upon the shores. 
At a few yards from the side the water is very clear, colourless, and 
odourless; but has a strong saline taste, rather bitter. Its specific 
gravity is 1:112; and its mean temperature 19° Centigrade (15° 
feaumur). The bottom of the lake near the centre is level, very 
firm, and sandy; whilst the shores present a bottom of black greasy 
mud, exhaling constantly an odour of sulphuretted hydrogen. This 
mud contains the remains of the numerous aquatic plants which 
cover nearly the whole surface of the water in the shallower parts. 
It is much used in cutaneous diseases, rheumatisms, scrofula, &c.* 
The mud is applied to the affected part, aud allowed to dry in the 
sun. This treatment is repeated several times in the day; and a bath 
is taken in the lake at night and morning. The Lake Balta-Alba 
appears to owe its origin to subterranean springs passing through 
some of the layers of salt spoken of above. Its water has been in- 
completely analysed: it contains chloride of sodium and sulphate of 
soda, with a little carbonate of lime and sulphate of magnesia. 
In 1858 I gave an account, in ‘ The Geologist,’ of the researches 
of Dr. Lewy, of Paris, upon the colouring matter of the emerald, in 
which it was stated that the emeralds of the Muso mine, in Mexico, 
contained a certain amount of organic matter to which they owe 
their colour. This interesting question has been lately examined 
again by Professors Wohler and Gustav Rose, and the result com- 
municated to the Paris Academy of Sciences. They do not deny the 
existence of about 14 per cent. of organic matter in the emerald ; but 
they find that the emerald does not lose its cclour by calcination, as 
stated by M. Lewy, but becomes opaque; moreover, that the emeralds 
of Muso contain 1:186 per cent. of chromic oxide, a quantity which 
the last-named author considers too little to account for the colour. 
Yo prove this point, MM. Wohler and G. Rose melted together 7 
grammes of colourless glass with13 milligrammes of oxide of chromium, 
and obtained a transparent, homogeneous, green glass, the colour of 
which was found to be identical with that of the emeralds of Muso. 
Vauquelin, when he discovered chromic oxide in the emerald, at once 
* T have lately had forwarded to my laboratory for analysis, two specimens of 
volcanic mud from the Island of Ischia, which is appled likewise with considerable 
success in various diseases of the skin. I shall be able to make known its compo- 
sition in the course of a short time.—T. L. P. 
