CHRONOMETRY. • 147 



increased resistance of the air, from its free motion being 

 impeded by the weight of the clock. 



Indeed, it does not seem that attraction could produce the Reason why 

 effect alluded to ; for, though the ball of the pendulum might *££& u 

 be retarded in its ascent, its motion would be proportionably ascribed to 

 accelerated on its return. attraction. 



I have been induced to trouble you with this, merely from 

 respect to Dr. Hornsby's memory, and not with the slightest 

 intention of depreciating the talents of Mr. Reid. 



I am Sir, 



Your obedient humble Servant, 

 H. K. 

 Ipswich, Dec. 6, 1812. 



REMARK. 



From the nature and tenor of Mr. Reid's communication I Additional 

 concluded, that his single weight descended either in front or obs.on Mr. 

 behind the ball, and not on one side of it ; and in this arrange- ^ icatTon" 

 ment its attraction would add to that of gravity, whether per- 

 ceptibly or not. I likewise requested his brother, who brought 

 the paper, to suggest that it might be desirable to make trial of 

 a temporary piece or mass, to be put on or taken off at pleasure, 

 in the place where the weight had been inferred to produce the 

 greatest acceleration $ and to keep the weight out of the limit 

 of disturbance j this would remove all suspicion of irregularity 

 in the train : And I would, from the ingenious observations of 

 my Correspondent, suggest farther, that the temporary piece 

 should be a thin shell of brass, with a solid core of lead ; which, 

 when taken out, would greatly diminish the attraction, but not 

 the impediment from increased resistance of the surrounding 

 air. 



SCIENTIFIC 



