106 On the Acceleration of Water Wheels. 
The workmen themselves attributed it to the moon ; prob- 
ably from its supposed influence upon the ebbing and 
flowing of the tides. But, as I conceive that it exerts but 
little upon the ocean, still less upon lakes, and none 
whatever upon a mill pond, I therefore suggested that it is 
- owing to the pressure of the atmosphere during the night ; 
the earth and circumambient air being rarified durin the 
day, the colder air above upon th going down of the sun 
condenses, and presses towards the earth. During the 
winter season the same result takes am in warm weather 
followed by cold, or the water is more directly acted upon by 
a body of ice upon its surface.* The assertion should there- 
pies have been made with a little modification, not that 
every night a mill (water-wheel) goes faster than it does 
during the day, but upon such nights, and during such 
monet as to peace the additional pressure of the at- 
mospae - 
3. a ao a letter from 
_the State of Maine, Dec. 6 1824. 
“i live j in "the vicinity of numerous saw-mills, a ais is 
the universal belief, that these mills move Sia in the 
here 
night than in the day, and that more work may be effected 
in a given time, during the former period. More than a 
year since I was Jed to perform some experiments, the re- 
sult of which is. that they do not move more rapidly in the 
night than in the. day- I had almost forgotten the subject 
until it was recently brought to view by. some remarks on 
the subject which I saw in the papers.” 
“Now it is always considered a mark of prudence to 
ascertain the existence of a fact, before we attempt to ex- 
plain it; and I am not cettain but my attempts to ascertain 
the existe nce of the supposed fact as to s Id be 
considered equally idle and unprofitable.” 
*This may be exemplified in a familias way by placing the mouth to the 
bung-hole of a barrel partly filled with liquid, in the head of which a hole 
se nay bored for a tap :—by blewing intothe barrel the jet of water is 
o the Editor, a in. 
