hk. H. Richards—Jet Aspirator for Laboratories. 415 
stated, a successful aspirator of this form must have true foam 
existing in its outlet tube o when it is at work, and it is evident 
that the larger this tube becomes relatively to w, beyond certain 
limits, the less will be the probability of our attaining a true 
foam. On the other hand, the smaller the tube o relatively to 
w the greater and more injurious will be the retarding force of 
friction. While keeping these two limits in sight the follow- 
mg experiments were made, the air being freely admitted. 
Aspirators of these sizes were tried. 
w? :07=1: 15 gave foam. 
: 20 ce eo 
w2:02=]1 
w*:o%'=1:24 “ tube of water. . 
w2:o2=1:28 * tc “ 
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followin eX) t made to ascertain, if 
the exact position of these lines of force. An aspirator 
