he driver doing something intentionally; whereas in
the automatic gear of Messrs. Massey and Lewis, of which an illustration
is annexed, there is nothing to cause damage or to interfere in any way
with the proper handling of the engines, and it is practically out of the
power of the driver to render the gear inoperative. It is here shown in
its simplest form as applied to the ordinary reversing and steam handles
of a winding engine, the only additions being an arm jointed to the top
of the valve spindle, with its connections to the shaft of the reversing
lever, and a disk receiving a suitable motion from the main shaft of the
engine. On the disk is a projecting piece or stop which is brought into
such positions, at or near the end of each journey, that the stop valve
cannot be opened, except slightly, when the reversing lever is not set
for winding in the proper direction, or when the cages have reached a
point beyond which it is undesirable that the engine driver should have
the power of turning on full steam. Thus, if one cage is at bank, the
driver cannot draw it up into the head gear suddenly; but after it has
been lifted slowly off the keeps or fangs, and the reversing lever thrown
over, the stop valve can be lifted wide open; and supposing that while
the engine is running the driver neglects to shut off steam in proper
time, then the projecting piece on the disk in traveling round, slowly
or quickly, and by steps according to requirements, will come in contact
with the driver, and so prevent an accident by bringing the reversing
lever into or beyond mid-gear.

Messrs. Lewis and Massey contemplate the use of governors in combination
with various forms of their automatic gear, so as to provide for every
imaginable case of winding, and also to avoid accidents when heavy loads
are sent down a pit; the special feature in their mechanism being that
when two or more things happen with regard to the positions of steam or
reversing handles, speed or position of cages in the pit, whatever it may
be necessary to do to meet the particular case shall be done
automatically.

* * * * *

THE WATER SUPPLY OF ANCIENT ROMAN CITIES.

[Footnote: An address by Prof. W.H. Corfield, M.D., M.A., delivered
before the Sanitary Institute of Great Britain, July 9, 1885.--_Building
News_.]

As the supply of water to large populations is one of the most important
subjects in connection with sanitary m