1 06 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 during the 

 day, the colder air above upon the going down of the sun 

 condenses, and presses towards the earth. During the 

 winter season the same result takes place 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- 

 fore 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 

 weather, as to produce the additional pressure of the at- 

 mosphere.'' 



3. Extract of a letter from to the Editor, dated in 



the State of Maine, Dec. 6, 1824. 



" I live in the vicinity of numerous saw-mills, and it is 

 here the universal belief, that these mills move faster in the 

 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 led 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 certain but my attempts to ascertain 

 the existence of the supposed fact as to saw-mills would be 

 considered equally idle and unprofitable." 



*This maybe exemplified in a familiar way by placing the mouth to the 

 bung-hole of a barrel partly filled with liquid, in the head of which a hole 

 has been bored for a tap : — by blowing into the barrel the jet of water is 

 increased. 



