nveniences. The passage of the gas
through a column of cold water is, of course, sufficient to condense it,
and clear it of these injurious properties; but this operation has for
its immediate effect the presentation of an obstacle to the flow of the
gas, and consequently augmentation of pressure in the retorts. In order
to obviate this inconvenience (which exists notwithstanding the use of
the best washers), exhausters are employed to draw the gas from the
retorts and force it into the washers. There is, however, another
inconvenience which can only be remedied by the use of a second
exhauster, viz., the loss of pressure after the passage of the gas
through the washer--a loss resulting from the obstacle presented by this
appliance to the steady flow of the gas. Now as, in the course of its
passage through the remaining apparatus, on its way to the holder, the
gas will have to suffer a considerable loss of pressure, it is of the
greatest importance that the washer should deprive it of as little as
possible. It will be obvious, therefore, that a washer which fulfills
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 centr