4 On Deal Pendulum Rods. 



direction of Mr. Gratiam, the diflerence is much less than 

 might be expected. 



The following variations of the daily rate of the Green- 

 wich clock were taken from Dr. Maskelyne's observations 

 of the sun. 



Tal>le of greatest Variations in the daily Rate of the transit 

 Clock at the Royal Observatory . 



Greatest an- 



Clock varies nual varia- 



from sidereal tion in the 



time per dailv rate of 



day. 



- 0-97/ 

 + 2-10) 



— 2-53/ 

 + 3-74i 



0-0]/ 



1793. April 4 to 15 .. 

 May 1-2 to 13 .. 



1794. February 25 to 26 

 December 18 to 19 



1795. January 3 to 4 . . 

 August 10 to 1 1 



1796. May 6. Raised the bob of the 



pendulum. 



1797. July 31. Ditto. 



1798. July 31. Clock was cleaned, 



and the con)pensation for 

 heat and rold increased. 

 1799- January 15 to 16 



Dtceinher 28 to 29 



1800. May 2 to 3 



December 3 to 4 



1766* May 6 to 7' 



August I'to 2 .... 



Now, the sum of the last column in the above table dl" 

 vided by 6, gives the mean annual variation. in the daily rate 

 of the transit clock at Greenwich for six years = 3-9". 



And thus the mean annual variation of my clock is found 

 for the sanre number of years = 5-n'\ Consequently the 

 transit clock at the Royal Observatory went only \-5\" per 

 annum nearer true time, than a clock with a pendulum rod 

 of wood. — Nor is this a matter that need astonish any one 

 who understands the construction of the two pendulums. 

 In ijje gridiron pendulum there is some friction, v^hich 



* See an account of the going of Mr. Harrison's watch, at the Royal Ob-, 

 servatory. 



ought 



0-87\ 

 J-84/ 

 04 ^1 

 4-16/ 



+ ^'o■i\ 



— 3-30/ 



2-71 

 4-GO 

 4-61 



