Account of a New Air Pump. 143 
time, an equation must be found shewing how much the mo- 
tion of the earth is affected by the attraction of the “ dis- 
tant centre.” But the apparent place of the sun is found 
without any such equation. It must be true then that the 
system does not move inany “orbis mundorum.” 
E. D. 
Williams College, March, 1824. 
Art. Kieshccount of a new Air Pump, in a letter to the 
aft, Editor from Joseph H. Patten. 
= Newport, R. I. Jan. 14th, 1824. 
Dear Sir, 
I enclose for vour inspection, the draught of a pneumatic 
pump, which I think, willin a considerable measure obviate 
the defects of those in common use. e construction is 
so simple that it will require but a small share of skill, or 
ingenuity to put it together, and it will be less liable to get 
out of repair than the pumps now in use. The valves which 
in other machines are a great source of difficulty, may be 
made larger and stronger, and the apertures, of course, will 
be more accurately closed, without at all affecting the de- 
gree of exhaustion. The vapour arising from the oil neces- 
sarily used in all pneumatic instruments, is in this complete- 
ly excluded from the receiver, and the vacuum in the ex- 
the brass work. The subjoined sketch, although not drawn 
by an adept in the art, will, | hope, give you an idea of it. 
Tt represents a vertical section of a table pump, supposed to 
be divided directly through the centre, with one half of the 
wood work, to which it is attached. . 
It is a number of months since I first thought of it; I 
then had one constructed with a barrel of sheet brass and 
the plate of the pump of tinned iron; it was very coarsely 
done, and the exhauster was filled with linseed oil, but not- 
Withstanding its roughness, it far exceeded my expecta- 
