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An Account and Defcription of three PENDULUMS invented 

 and conJiruBed by JOHN CROSTHWAITE, Watch and 

 Clock Maker, Dublin. 



-f IG. I. reprefents a pendulum, with a fimple mode of compen- Read Nov, 

 fation, which has now been going eighteen years, much more '' '' '" 

 accurately than could be expeded in fo very unfavourable a fitua- > 



tion : the firft ten years againft a lath and plaifter partition, within 

 three feet of the external wall, and the fame diftance from a hall- 

 door, the frequent ihutting of which muft have very much dif- 

 turbed its vibrations ; the laft eight years, againft an external 

 wall only three feet from the ftreet ; which, though a much 

 better fituation than the former, yet even here it was liable to 

 have the ifochronifm difturbed by the carriages almoft conftantly 

 pafling. 



A and B are two rods of ftcel forged out of the fame bar, at 

 the fame time, of the fame temper, and in every refped fimilar. 

 On the top of B is formed a gibbet C ; this rod is firmly fupported 

 by a fteel bracket D, fixed on a large piece of marble E, firmly 

 fet into the wall F, and having liberty to move freely upwards 



between 



