esium salts are abundant in sea-water, and in the waters of
evaporating enclosed coral lagoons and of many bitter lakes. Calcite is
more soluble than dolomite in water saturated with carbonic acid and
would tend to be slowly removed from a limestone, while the dolomite
increased in relative proportion. Dolomite also being denser than
calcite may be supposed to replace it more readily when pressure is
increased. These and many other factors probably co-operate to effect
the transmutation of limestones into dolomites.

Examples of dolomitization may be obtained in practically every
geological formation in which limestones occur. The oldest rocks are
most generally affected, e.g. the Cambrian limestones of Scotland, but
the change occurs, as has already been stated, even in the upraised
coral reefs of the Indian and Pacific oceans which are very recent
formations. It is very interesting to note that dolomites are very
frequent among rocks which indicate that desert or salt-lake conditions
prevailed at the time of their deposit. The dolomite or magnesian
limestone of the English Permian is an instance of this. The explanation
may be found in the fact that the waters of bitter lakes are usually
rich in magnesium salts which, percolating through beds of limestone,
would convert them into dolomite. Among the most famous dolomites are
those of the Dolomite Alps of Tirol. They are of Triassic age and yield
remarkably picturesque mountain scenery; it is believed that some were
originally coral reefs; they are now highly crystalline and often
contain interesting minerals and ores. The galena limestone of the
North American Trenton rocks is mostly a dolomite.

Dolomites furnish excellent building stones, and those of the north-east
of England (Mansfield stone, &c.) have long been regarded with great
favour on account of their resistance to decomposition. They vary a good
deal in quality, and have not all proved equally satisfactory in
practice. Part of the Houses of Parliament at Westminster is built of
dolomite. (J. S. F.)

DOLOMITES, THE, a mountain district in the South Tirolese Alps, though
sometimes it is erroneously considered to form part of some other chain
than the Alps. The distinguishing feature of this district is that it is
composed of magnesian limestone, which rises in peaks of a most singular
degree of sharpness and streaked by veins of the most startling colours.
Nowadays it has become well known to tou