L fart of a Letter from Mr D. Papin to Dr Vrcd^ 
rick SlarCj FellotP of the College of fhyficiam and 
of the ^yal Society^ concerning oil Improy$mm of 
the HtSim bellows ^ &c» 
I Am bufie at prefent for a Coal-mine, which hath been 
lett ofFbecaufe of the impurity ot the Air : *I have 
therefore improved the Bejfian Bellows : 1 don't queftion 
but you have feen that new contrivance, printed Lipji£ in 
AUk Eruditorum arj7io 1 699. with this Tide, Rotatilif 
SuUor & Prejfor H^jfiacus : And it may be apply'd for 
Wind as well as for Water. At that time the fhape of 
the Tjmpanum v^as Cylindric, as may be feen Fig. i, 
Vi^here D A F C is the circumference i C P, D P, A P, ara 
th^ Radii which bear the Wings C m, D n, A o : C E i^ 
the aperture through which the Wind muft be driven in 
the diredion of the Tangent CB : And it may be obferv'd 
that v^hen the Engine is woriing, every Wing from the end 
of the aperture E, till it comes to the beginning of the fame 
aperture C, drive always the fame Air, with the fame 
fwiftnefs, and at the fame diftance from the Center : So. 
that in perufang all that circumference, the Air doth find 
feiiftance by friftion, and gets nothing at all. I dd there- 
fore now make the circumference of the Tympanum in a 
Spiral fliape, which is to be feen Fign 2. where the Spiral 
circumference is A FG B, the Radii are AP, CP, DP, &c. 
The Wings are AM, CN, DO, d'^*. The aperture is 
AB. And it is to be obferved,^ that every Wing in going 
yound drives nev\r Air, becaufe the Air v^hich is firft in 
motion finds place 10 recede from the Center towards the 
Spiral circuotference | and fo it gives room to new Air to- 
come 
