244 
MR. J. J. MANLEY ON THE APPARENT 
A large glass jar, J (fig. 2), was fitted so as to form a blower, the exit tube of a 
water pump being made to enter through a side tubulure near the bottom ; the desired 
air pressure, p, was provided by suitably proportioning the length of stem of the 
funnel F. By duly regulating the working of the pump the jar was kept full of air ; 
any air entering in excess of that actually drawn off through the tap t escaped with 
the water through the funnel. The bulb 
of the funnel should be large, and it must 
communicate freely with the external air, 
otherwise the attached waste pipe comports 
itself as a water pump and so greatly 
interferes with the uniform delivery of air 
through t. On stopping the supply of 
water, that which still remains in the jar 
automatically syphons off through the 
pump and its air tube ; consequently the 
apparatus is always ready for immediate 
use. On leaving the jar by way of the tap 
t, the air is by means of two other taps, 
situated beyond the first, divided into two 
equal streams, each of which is then driven 
through a Drecshel wash-bottle charged 
with concentrated sulphuric acid ; the acid 
serves a two-fold purpose; it removes the 
greater portion of the contained moisture 
and also indicates the rate at which the 
air is passing. As the partially dried air 
emerges from the wash-bottles, each stream 
enters its own set of 3 purifying tubes ; the 
first half of each set is packed with small 
fragments of soda-lime and the second half 
with similar pieces of calcium chloride; 
finally, the air is allowed to filter through plugs of glass wool and is then conducted 
by glass tubing through one side of the balance case to the interior of the copper 
cylinders which surround the pans and stirrups. The glass air-tubes were passed 
through niches cut in the upper edges of the cylinders, their free ends being bent so 
that the air streams were delivered centrally and downwards. 
The apparatus just descril^ed enabled us to subject any objects, the masses of which 
we desired to subsequently compare, to a very perfect washing with air freed from 
carbon dioxide, moisture and dust ; in fact, we were now, for the first time, in a position 
to weigh an object under well-defined and easily re-producible conditions. The efficacy 
of the newly devised method was now put to the test; for this purpose another pair 
