1894.] on the Newtonian Constant of Gravitation. 



Summary of Results hitherto Obtained. 



357 



Approximate 

 date. 



1737-40 



1774-76 



1855 

 1821 

 1880 

 1854 

 1883 

 1885 



1797-98 

 1837 



1840-41 

 1852 

 1870 

 1889 



1879-80 



1878-90 



1884 



1886-88 

 1889 



Experimenter. 



Bouguer 



Maskelyne and Hutton 

 James and Clarke 



Carlini 



Mendenhall 



Airy 



Von Sterueck 

 Von Sterneck 



Cavendish 



Beich 



Baily .. 



Beich 



Coruu and Bailie 



Boys 



Von Jolly 



Boynting 



Konig, Bicharz, and 

 Krigar Menzel. 



Wilsing 



Laska 



Method. 



Blumb-line and pen- 

 dulum. 

 Blumb-line 



Mountain pendulum . , 



" * ' 



Mine pendulum 



Torsion balance 



Common balance 

 Pendulum balance 



Eesult. 



A 

 Inconclusive 



4-5-5 



5-316 



4-39-4-95 



5-77 



6-565 



5-77 



About 7 



5-448 



5-49 



5-674 



5-583 



5-56-5-50 



In progress 



5-692 



5-493 



(5-46-5-52) 



In progress 



5-579 

 In progress 



constructed that I can tell precisely where every gravitating particle 

 is placed. In the design of this apparatus I have been, as every one 

 will admit, bold — most would have preferred the word reckless ; bat 

 knowing the truth of the principles which I had developed, and 

 having faith and confidence in the quartz fibre, I deliberately chose 

 to reduce all the dimensions to an extent which caused the forces, 

 and especially the couples, to be insignificant in comparison with 

 any which had been within the reach of the experimenter hitherto. 

 The whole difficulty of Cavendish, Reich aucl Baily had been to 

 measure so minute an effect ; instead of increasing this I diminished 

 it enormously, being satisfied that I should be able to make a pro- 

 portionately more accurate measure by so doing. Cornu reduced the 

 dimensions to one-quarter; I have reduced the chief oue to one- 

 eightieth. Cavendish had a force equal to 1/3650 grain's weight to 

 measure; I have less than a five-millionth. By the use of the long 

 lever, Cavendish had the effect of a force of 1/100 grain's weight on 

 an arm an inch long ; I have less than a twelve-millionth of a grain 

 on an arm of that length. His forces were fourteen hundred times 

 as great as mine; his couples or twisting forces were a hundred 

 and twenty thousand times as great. One advantage gained by the 

 use of small apparatus, in which alone the attracting balls can be 

 made large compared with the length of the beam, is the increased 



