Theory of the Pneumatic Paradoz. 313 
in mercury contained in a basin supported in the upper part of the 
box. Having forced into a condensing chamber, by means of a 
syringe, three or four times as much air as it naturally contained, 
he directed a very rapid current through the tubes A and B, and 
the mercury was depressed from C to D, more than two inches, 
in consequence of the rarefaction which the current produced in 
the air of the box. 
Experiment I. In order to determine to what degree air can be 
condensed by means of the mouth and lungs, I poured a quantity 
of mercury into a glass tube, bent into the form of the letter U, 
and furnished at one end with a brass cap, stop-cock, and mouth- 
piece. The greatest difference that could be produced in the 
height of the mercury in the two branches of the tube by blow- 
ing through the stop-cock, was found, in a series of trials made 
by half a dozen able-bodied men, to vary from two and a half to 
nearly four inches. This result shows, that the degree of con- 
densation producible by this means, ranges from a twelfth to less 
than a seventh of an additional atmosphere. ‘The condensation 
producible by blowing through a tube presenting no obstruction 
to the escape of air, is obviously much less. One of the individ- 
uals mentioned above was able to exhaust fourteen fifteenths of 
the air from a tube having the lower end immersed in mercury, 
and the other furnished with a stop-cock, as was shown by the 
rise of the mercury in it to the height of twenty eight inches. 
Experiment If]. Make a cylindrical tube of tissue paper, about 
three fourths of an inch in diameter and five or six inches 
long, and fit into one end of it a circular piece of wood, having 
a hole in its centre one quarter of an inch in diameter. On blow- 
ing through the hole the tube will collapse. On blowing through 
a metallic tube of the same size, having a similar circular piece 
of wood in one end, and lateral holes, the flame of a lamp will 
be drawn into the holes. In both these cases the current from 
the mouth communicates a share of its outward motion to the 
lateral portion of air with which it comes in contact, and being, 
as has been already shown, but slightly condensed, becomes more 
~ rare, when it expands to fill the tube, than the external air; which 
is prevented from rushing in at the end of the tubes to restore 
the equilibrium, by the impulse of the blast. Ai 
Experiment IV. Lateral holes were made ina cylindrical brass 
tube, about five inches long and three sixteenths of an inch in 
