I. On the Newtonian constant of gravitation

Abstract

In a paper on the Cavendish experiment, published in the ‘Proc Roy Soc,’ vol 46, P. 253, I showed how the famous experiment of Cavendish could be transformed in several particulars, so that greatly increased delicacy and accuracy would be obtainable. The experiment is so well known that there is no occasion to describe the apparatus which Cavendish employed, or the subsequent work of Reich, Baily, or Cornu and Baille. It is sufficient to state that, owing to the extremely small value of the Newtonian constant of gravitation, all these experimenters made use of balls as large as they conveniently could, so as to increase the force of attraction as much as possible, and of a lever as long as they could, so as to increase the effect of the force in producing torsion. However, Cornu realized that if he could keep the period the same by the use of a sufficiently fine torsion wire, and reduce the dimensions of the whole apparatus, the angle of deflection would not be reduced but would remain the same. Cornu also introduced refinements which have made the behaviour of his apparatus far more consistent than that of any which had preceded it.