348 
THE GEOLOGIST. 
Fossil Teichechus. — " The teetK of the sea-horse are frequently found 
in many places of the Arctic turf-marshes bordering on the Frozen Sea, 
and they are so fresh that they are sold in commerce for ivory. In the 
Gulf of Penschin there was one of these teeth dug out that was 8^ lbs. in 
AAeight, and another in Kamtchatka weighing 5^ lbs. (P. Nordmann, 
Beytr.) A tooth of a bluish colour was found at the mouth of the Tagil." 
— Extract from Georgi, (Nat. Hist. Eussia) ' Beschreibung des E-ussischen 
Eeichs,' vol. iii. p. 591, by S. J. M. 
Salt Deposit at New Ibeeia. — The rock-salt at this place in Louisiana 
is of the most extensive and wonderful description, and of great purity. One 
American account says : — " Imagine the granite quarry of Massachusetts, 
or the marble quarry of Vermont, to be solid deposits of pure rock-salt, 
clear and transparent as so much clear white ice in one solid inexhaustible 
mass underlying the earth, and you will then acquire an imperfect idea of 
the vastness of this salt formation." 
Natural Formation of Carbonate of Soda. — In the ' Pharmaceutical 
Journal' for July, Dr. Haines, of Grant College, Bombay, gives an account 
of the natural production of carbonate of scda in the neighbourhood of 
Aden. It occurs in the form of irregular, colourless, partly crystalline 
masses, apparently of two distinct portions : one a brilliant, confusedly 
crystalline mass, amongst which the angles of cubical crj'stals could be 
observed ; the other, a white amorphous substance, of a greasy feel and 
soapy odour, very similar to crude borax. By analysis, the composition 
was given as : — 
Neutral carbonate of soda 5105 
Common salt, with traces of sulphate of soda and 
chloride of magnesium 21*94 
^Vater and organic matter 19'66 
Sand 4"35 
100-00 
Captain Playfair, Assistant Political Eesident at Aden, states that this 
substance is found all along the coast to the east of Aden to an extent of 
perliaps ten miles, and its quantity is practically unlimited. It is usually 
found in hollows behind (or bej^ond) high-water mark to which the sea- 
water has access by percolation. There is no demand for it at present, 
but some months ago, sixty to seventy camel-loads a day were brought 
into Aden, and met with a ready sale at 2\ rupees per ten maunds (equal 
to two shillings a hundredweight). The only use made of it is to mix with 
snuff, to increase the pungency ; rarely, too, it is used for washing clothes. 
It is variously called by the Arabs Dukduka, Hurka, and Kara. 
From the valuable paper published by Mr. H. J, Carter in the Trans- 
actions of the Bombay Branch of the Eoyal Asiatic Society, on the 
Geology of Arabia, it appears that the whole of the south-east coast of 
Arabia, from Eus-al-Had to Bab-ul-Mandib, is capped with nummulitic 
limestone, pierced at frequent intervals with basaltic effusions, and in 
many places elevated so as to form lofty and abrupt cliffs, in which, be- 
neath the limestone, other formations are visible. As a result of this for- 
mation, the shingle on the coast consists mainly of limestone ; and although 
no specific description of the coast immediately to the east of Aden has 
been given, there is no reason to doubt that the same peculiarities prevail 
there. It is then to the percolation of sea-water through a stratum of 
fragments of limestone that we must attribute the production of the car- 
bonate of soda, by which percolation, probably, a partial interchange of 
