exhausting and blowing simultaneously, the efficiency in each case being
always the same. Any bends in the conduit affect the result to a very
slight degree, and the ventilator may be used with advantage when the
conduit is divided as in Fig. 4, in order to get the fresh air to
different points. The ventilators are easily fixed to the air conduits.
If they are to be connected to zinc air pipes, the pipe is simply slipped
over the point, L. in Fig. 1, and if to wooden conduits the apparatus is
simply put into them, and if no other support is required. Furthermore,
they are so light that it suffices for one man to fix them or change
their position.

Messrs. Korting Bros. advance the following claims for this mode of
ventilating mines: Certainty of action, no moving parts whatever,
and, consequently, no need of lubrication; no need of attention.
--_Mech. World_.


* * * * *




ON REMELTING OF CAST IRON.


From trials conducted by Ledebur, it appears that cast iron is rendered
suitable for foundry purposes--i.e., to fill the moulds well and to yield
sharp and definite forms free of flaws, to be cut with a chisel, and
turned on a lathe--through a certain percentage of graphite, whose
presence depends on that of carbon and silicium. Cast iron free of