424 HORARY VARIATIONS OF THE BAROMETER. 



at rest, it is plain that it will begin to fall as soon as the force of the superior 

 parts of the air begins to spend itself on the inferior, and when all motion down- 

 wards has ceased, the mercury will again be pressed by the natural weight of 

 the atmosphere, and so stand at thirty inches. In this situation the sun will rise' 

 upon it, and the same fluctuations will be renewed. 



„T3 .. - "J- I*- ESPY. 



"Philadelphia, March, 1, 1827." 



