Remarks on Mr. Patten’s Air-Pump. 275 
Art. XV 1.—Remarks on Mr. Patten’s Air-Pump, 
(described in the last number) 
. F. Dana. 
‘To rue Enrror, Dear Sir, 
ane me, that the Poicidedce seems to fave been concerted. 
There was one difference between the construction p 
by myself and that proposed by Mr. P. and by whic 
‘hoped to accomplish a great desideratum in the construc- 
tion of air pumps. viz. to dispense with all valves, oil, &c. 
&c. between the air the working piston and the receiver. 
This I hoped to effect by means of a stop-cock, which the 
accompanying sketch will explain, and which is to be placed 
between the glass globe (K Mr. Patten’s drawing) and the 
receiver, and which [ consider as much more simple 
the ee proposed by Mr. P. 
the receiver on the plate of the pump, a. (see 
3 the stop-cock, in which there are two passages, viz. 
hich in the present position ofthe apparatus allows 
t which, if the stop-cock was turned 
‘ ) s soaldc open a communication between the atmos- 
J phere and the receiver A ; the other passage C in the pre- 
< and the receiver A and at the same ti 
tmosphere and the fapparains 
would be cut off. Now suppose the apparatus to be in the 
| represented by the drawing and the mercury was 
rising in the globe by the action of the piston in Mr, P’s 
ommunication between the atmosphere and the 
