THE KAMSDEN DIVfDlNG ENGINE. 739 



instruments that are brought into coiui)arisou by iSir George Shuck- 

 burg, after having reduced theui all by one rule, viz : 



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

 extent to divide the a[)pareut error equdlly between them. 



"They are exi)ressed in parts of an iuch aud follow each other in the 

 order of their accuracy. 



Sir George Shuckburg's .l-feet standard ()()(>1(;5 



General Koy's scale of '12-inch standard OOOlMO 



Sir George's ecpiatorial, 'Jl-ineh standard ('0()27u 



The Greenwich (piadrant, 8-feet standard . . .00()4<i5 



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



The Koyal Society's standard,* 92-inch standard 0007i)5 



" Forthejustness of theabove statement [consider my name i)ledged." 



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

 for astronomical aud 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 abouf 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. 



