THE RAMSDEN DIVIDING ENGINE. 739 



instrunieuts that are brought iuto comparison by Sir George Shuck- 

 burg-, after having reduced them all by oue rule, viz : 



" Allowiug each of the two poiuts which bound the most erroneous 

 extent to divide the apparent error equally between them. 



"They are expressed in parts of an inch and follow each other in the 

 order of their accuracy. 



Sir George Shuckburg's o-feet standard 000105 



General Koy's scale of 42-inch standard 000240 



Sir George's equatorial, 24-inch standard C00273 



The Greenwich quadrant, 8-feet standard 000405 



Mr. Aubert's standard, 5-feet standard „ 000700 



The lioyal Society's standard,* 92-inch standard 000795 



" For thejustness of the above statement I consider my name pledged." 



I am informed by recent travellers in China and Japan that the ciicles 

 for astronomical and other instruments are still divided by hand, un- 

 aided by machinery. 



The dividing engine at the Coast Survey, Washington, made by 

 Troughton, was made automatic by Joseph Saxton about 1855 ; it was 

 re-constructed about 10 years ago by Fauth & Co., of Washington, 

 who have at their establishment a dividing engine for which they claim 

 great accuracy. 



Thus have the mechanicians for a century kept pace with the de- 

 mands for accurate instruments. 



* This is the same which Mr. Bird used in dividing his 8-feet mural quadrant aud 

 was presented to the Royal Society by Mr. Bird's executors. 



