the best conditions as far as regards the cleaning of the gas will be
absolutely perfect if it does not present any impediment to its flow.
Such an appliance is that which is shown in the illustration on next
page. Its object is, while allowing for the washing being as vigorous
and as long-continued as may be desired, to draw the gas out of the
retorts, and, having cleansed it perfectly from its deleterious
properties, to force it onward. The apparatus consequently supplies the
place of the exhauster and the scrubber.

The new washer consists of a rectangular box of cast iron, having a
half-cylindrical cover, in the upper part of which is fixed a pipe to
carry off the gas. In the box there is placed horizontally a turbine,
the hollow axis of which serves for the conveyance of the gas into the
vessel. For this purpose the axis is perforated with a number of small
holes, some of which are tapped, so as to allow of there being screwed
on to the axis, and perpendicularly thereto, a series of brooms made of
dog grass, and having their handles threaded for the purpose. These
brooms are arranged in such a way as not to encounter too great
resistance from contact with the water contained in the vessel, and so
that the water cast up by them shall not be all thrown in the same
direction. To obviate these inconveniences they are fixed obliquely to
the axis of the central pipe, and are differently arranged in regard to
each other. A more symmetrical disposition of them could, however, be
adopted by placing them zigzag, or in such a way as to form two helices,
one of which would move in a particular direction, and the other in a
different way. The central pipe, furnished with its brooms, being set in
motion by means of a pulley fixed upon its axis (which also carries a
flywheel), the gas, drawn in at the center, and escaping by the holes
made in the pipe, is forced to the circumference of the vessel, where it
passes out.