426 R. H. Richards—Jet Aspirator for Laboratories. 
vapor so long as water is used in it. I have made one attempt 
to produce a mercury pump to work upon the same principle, 
but the instrument was not a perfect success. It will need study 
to secure its best form, and to ascertain whether it can be made 
more available than Sprengel’s fall pump, which is now com- 
monly in use. 
n experiment was made to ascertain whether the form of 
the converging cone which connects the reservoir ¢, and the 
constricted point a, fig. 8, influences in any way the success of 
the aspirator. ‘The form of aspirator used was that represented 
in fig. 10., which removes the converging cone entirely. The 
data of the experiment were :—w= 056”, a= 080”, a?:w? =2:1. 
The barometer stood at 7784. 
Air tension. Water pressure. 
745-400 2406-9™™ 
742°4 1621°2 
737° 1505°5 
In the second experiment the aspirator was about at its limit, 
i. €., an increase of water pressure would not materially increase 
its power, while a slight decrease would seriously impair its 
power, which gives us an opportunity to compare this form of 
aspirator by means of Table [V with an aspirator of the ordin- 
form : 
Ratio Ratio 
Air ten. to water pres. w?®. a’. 
a a 
a iy! 12 
The difference between these two numbers 2°09 and 2°17, is 
In aspirator fig. 10, 
oe oe “ 3, 
fluence the quantity of air carried by the instrument. I find 
ts. 
Prof. Mixter informs me that Fechner of Berlin uses a jet 
aspirator differing in form and principle from my Giffard’s 1n- 
jector experiment, only in the fact that he fills the cone ao with 
foam by placing o in a beaker of water. 
