ON THE IRREGULARITIES OF TIME. 77 



Thefe contrivances, how ingenious foever they may appear of little pracVi- 

 in theory, have not aufwered any good purpofe in pradice ; cal utlllt y« 

 but, what may be impracticable to perform by one method, 

 may not be found to by another. 



The fpring by which the pendulum is fufpended feems ca- Propofed remedy 

 pable of receiving fuch improvement, as would render the JjjJJSTSwfc. 

 long and (liort vibrations ifochronal, without any other altera- bility of the 

 tion in the mechanifm of the clock. This improvement con- r P™$ of fuf P ett * 

 fifts in cutting the fpring broader at the top than at the bot- 

 tom, that it may not bend totally at the point of fufpenfion. 

 The pendulum would, in that cafe, when in motion, become 

 (horter at the ends of the arc, confequently it would no longer 

 vibrate in the arc of a circle, and on this account there is 

 fome reafon for fuppoiing that the long vibrations would be 

 performed in lefs time than they were before. 



When this method is put in practice, the fpring mould be Method of ao, 

 Hiade fo broad at the point of fufpenfion at firft, that the long JU ment * 

 vibrations may be performed in lefs time than the fhort ones, . 

 and then made narrower till all the vibrations be performed in 

 equal times. But I fuppofed that this method would be at- 

 tended with much trouble, and that it would be better to re- 

 move the caufe than to counteract its effects. 



When I made obfervations on the pendulum above-men- Influencing 

 tioned, I found that it was much influenced by the weather. caulc » 

 In cold and moift weather it moved through a larger arc, than 

 when the atmofphere was dry and warm. 



As all metals alter their dimeniions, and confequently their fuppofed to ope- 

 elaftic force by heat and cold, it follows that that part of the *** ^ the 

 clock called the crutch, would act more forcibly on the pen- 

 dulum in cold weather than in warm j and it feems probable, 

 that this variation would be greater in a weak crutch than in a 

 ftrong one. 



About feven years ago having a regulator made by Mr. Experiment 

 James Bullock, of Holborn, and being defirous of putting m y w^h a regulator. 

 theory to the teft of experience, I had the crutch made ex- 

 ceedingly flrong, and firmly connected with the pallats, that 

 the maintaining power of the clock might be communicated to 

 the pendulum uniformly in all flates of the atmofphere. The 

 clock cafe is made very thick of folid mahogany, and upon 

 the rifing board *, which is two inches thick, Jftands an an- 





* The board on which the wheel -work ftands. 



