938 Wisconsin Academy of Sciences , Arts , and Letters. 
at a convenient angle for filling and emptying. In figure 7, a 
more compact form of the apparatus is shown. In the latter, 
the long tube is replaced by an air pump. 
These forms of pressure percolators were mentioned in con¬ 
nection with the preparation of the oleoresins by Mohr (1854) 
in his Commentary on the Prussian Pharmacopoeia. 
