262 - The American Naturalist. [March, 
The Ossete villages, built upon summits, are stated to abound in inter- 
esting antiquities. 
Tue Brack Sea.—A hydrographical exploration of the Black Sea, 
recently conducted by the Russian Government, has proved that the : 
waters of that large area exist under anomalous conditions. The 100 
fathom line follows the coast outline closely save in the north-west 
where it crosses with a slight northern inflexion, from Varna to the 
Crimea. From this the bottom descends at the tolerably steep gradient 
of twelve degrees to a depth of 500 fathoms, and from thence with a 
slighter inclination to 1,200 fathoms. The 1,200 fathom line encloses 
an oval in the center, with 1,219 to 1,227 fathoms as its greatest 
depths. : 
The upper stratum of twenty-five fathoms changes in temperature 
with the seasons; between this and 100 fathoms the coldest water, as 
low as 44° is found, while below 100 fathoms the constant temperature 
is 48°. In August the upper surface of the cold layer sinks to from 
thirty-five to fifty fathoms. The vertical circulation of the water is 
limited to the upper one hundred fathoms, and there is no trace of 
organic life below this level. The lower layers contain much sulphur- 
etted hydrogen, besides sulphates of alkaline and earthy metals, yet 
the principal reason of the absence of life is probably the deficiency of 
oxygen in a dissolved state. The bottom from ten or twenty to a hun- 
dred fathoms is covered with a light gray mud; from 100 to 800 fath- 
oms the mud is dark gray, and at greater depths it assumes a bluish 
tint through the prevalence of carbonate of lime. Remains of brackish 
water mussels, of which species some still live in the Caspian, while 
others inhabit the rivers flowing into the Black Sea, are found at 
depths of from one to six hundred fathoms. It has been assumed that 
at the beginning of the Quaternary and end of the Pliocene periods, 
the Black Sea was a brackish lake, without any communication with 
the Mediterranean, and that at the end of the glacial period the very 
salt waters of the Mediterranean bursting in through the newly opened 
Bosphorus, accumulated at the bottom, prevented circulation, and 
annihilated the brackish water fauna. ` ' 
THE MEDITERRANEAN.—The depths of the eastern Mediterranean 
have been explored by the Austrian expedition in the Pola. A depth 
of 4,400 metres was found in 35° 44’ 20” N., and 21° 44’ 50” E. long., 
at a distance of only about fifty knots from Cape Matapan. A few 
miles farther eastward 4,080 metres was found—these are the greatest 
