JOUR N A L 



OF 



NATURAL PHILOSOPHY, CHEMISTRY, 



ANO 



THE ARTS. 



MAT 1798. 



ARTICLE I. 



0« the maintaining Power in Clocks and Watches. 

 [Concluded from Page 419, Vol. I.] 



A F we fuppofe the pendulum of a clock to prcfcrve its length invariable * during all the 

 changes of temperature to which it is expofed, its vibrations will meafurc equal portions 

 of time fo long as the arc of vibration continues the fame. The refiftance of the air and 

 of friflion are prevented, by the maintaining power, from dcftroying the vibration. This 

 power may be applied in different parts of the arc ; and may, according to circumftances, 

 render the time of vibration either {horter or longer, or it may fimply maintain it without 

 altering the time. Whether it alter the whole time or not will be of no confequence to 

 the performance of the regulated machine, provided the effeft of the maintaining power 

 is itfelf fubjedt to no variation. For the thing required is, that all the vibrations, when 

 once brought to an accurate adjuftment, fliould continue invariable. It is therefore 

 cflential to a good time-piece, either, i. that the maintaining power itfelf fliall not vary; 

 or, 2.. that it (hould be applied to the pendulum or balance in fuch a manner, as that in 

 all variations of the power itfelf the time of vibration may continue the fame ; or, 3. that 

 it {hall a£l during a very fmall part only of the time of vibration, in order that the cffcdl 

 of its variations may be lefs. 



* Philofophical Journal, I, page 58. 

 Vol. II.— Mat 17^8. H When 



I 



