boullay's filter, etc. 
3 
or other fluid, you cause to be displaced from the substance 
acted upon, without intermingling, a like quantity of the vehicle 
replete with its active soluble principles, which escapes by the 
inferior part of the funnel. So that after the absorption by 
the vegetable powder of a certain quantity of liquid, every 
drop added to the surface causes one to fall from the bottom, 
each affusion driving the one before it through the incoherent 
mass, causing it to take up in its passage some soluble matter, 
and forming throughout the process successive strata of 
different degrees of strength, being less highly impregnated 
at the top, and more highly charged as it approximates to the 
bottom of the funnel. 
Great attention had been directed to the importance of 
Real's filter press, which consists of a tin box made to receive 
a saturated powder, upon which a vertical tin tube is made to 
fit, capable of containing a narrow but elevated column of 
liquid, to which was attributed its great power. Its supposed 
advantage was said to reside in its capacity to displace a 
quantity of liquid contained in the saturated powder, propor- 
tionate to the height of the column of liquid in the tube. 
Particular stress being given to the high pressure. 
That any advantage is to be derived from the high pressure, 
the Messrs. Boullay are unprepared to acknowledge, the 
results of their experiments not justifying them in the belief. 
But, while unwilling to grant this, they accord to it the merit 
of enabling you to withdraw, even to the last drop, from a 
saturated powder, all its menstruum holding the active prin- 
ciples, by the employment of the smallest quantity of vehicle, 
an advantage not possessed by any other means in ordinary 
use. The limpidity of the products, the superior quality and 
abundance of extract which Real's filter allows you to obtain, 
they also pass to its credit. 
Operating independently of the filter of Real, they expe- 
rienced, in a most satisfactory manner, the same benefits, 
without other pressure than the simple weight of the quantity 
of liquid necessary for displacement. Since then the whole 
mechanism of the process resides in this, a column several 
