362 A. E. Foote—Jagn Vacuum or Filter Pump. 
The valve is constructed as follows: A cylindrical metal 
plug about one inch long, and of such diameter as to slip 
easily within the tube B, is cut away at one end (as shown in 
fig. 2, where it is represented in section, with a portion of tube 
B), leaving a tongue of metala. This tongue of metal is driven 
own upon a flap of sheet caoutchouc, about 1 millimeter in 
thickness, 6, which is thus held upon the bevel of the plug 
and covers the two channels, ¢c, one of which is seen in section. 
I will here make note of a simple arrangement devia 
one of my students, Mr. F. D. Whitney, which quickens 
ses. 
; ehind the sink fasten 4 ner 
t 
: rtional 10° 
bottle. The vacuum produced is of course Pp we its con’ 
ro 
the column of water supported in the thistle tube a 
nections, 
