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