The rotary blower used in these experiments for maintaining the
ventilating current of air has given the greatest satisfaction. It is a
so-called positive blower and capable of producing at the outlet
considerable pressure and at the inlet a vacuum of several inches of
mercury. At a speed of 230 revolutions per minute it delivers the air at
a pressure of 43 millimeters of mercury, forcing it through the
purifying vessels at the rate of 75 liters per minute. This rate of
ventilation has been established as being satisfactory for all
experiments and is constant. Under the pressure of 43 millimeters of
mercury there are possibilities of leakage of air from the blower
connections and hence, to note this immediately, the blower system is
immersed in a tank filled with heavy lubricating oil. The connections
are so well made, however, that leakage rarely occurs, and, when it
does, a slight tightening of the stuffing-box on the shaft makes the
apparatus tight again.