86 Description of an Air Pump. 
After testing the utility of these improvements for about five 
years, being desirous that all using furnaces might avail them- 
selves of them, I have sent this communication for insertion in 
your interesting record of the daily improvements going on in ae 
arts and sciences. 
Art. Vil—Description of an Air Pump of a very simple con- 
struction, which acts both as an erhauster and condenser ; by 
OHN Jeusisto x, A. M., Professor of Natural Science in the 
Wesleyan University, Middletown. 
Tue last No. of this Journal* contains a description of a very 
ingenious air pump invented by Dr. Hare, Professor of Chemistry 
in the University of Pennsylvania, which is capable of perform- 
ing on a much larger scale precisely the same operations as the 
one I am about to describe, but in quite a different manner. The 
“next day San I had aastrieted with Messrs. Brown & Francis, in 
New York, for this air pump, which is now in possession of the 
Wesleyan ‘Univeiity: I had the pleasure of viewing = She 
in his laboratory in Philadelphia. : 
This pump, as will be seen by the figure, has two bitiele in 
which the pistons are worked precisely as in those in common 
use, and, in general, it is constructed in a similar manner. The 
pistons, however, are solid, and at the base of each barrel are two 
valves, one opening upward and the other downward. In the 
center of the firm piece of mahogany, which forms the base of 
the instrument, are two brass tubes, which are seen in the figure 
at A and B, by the removal of the plate of brass D. Of these 
tubes, A communicates with the valves—one in each barrel—that 
opens upward, and B with the valves that open downward. Now 
when either of the pistons descends, the air in the barrel below it 
will of course pass out through the downward opening valve 
and tube B connected with it; and when it is again raised, the 
air will pass in through the tiibe A and the upward opening valve. 
At the center of the disc I’, is an aperture, as in common aif 
ee into which a tube may be screwed, and directly be: beneath 
ees 
_* Vol. xxiii, page 237. 
