The discovery of the light nuclei Hx2 Hi3 He23 has provided additional and much-needed material on which to base and test any theory of the structure and interaction on nuclear particles. The properties of these nuclei which are best known are their masses, the latest values of which are the following: no1 1-0083 Hxa 2-0142 Hx3 3-0161 He23 3-0172, assuming the validity of the mass scheme proposed independently by Oliphant, Kempton, and Rutherford,+ and by Bethef (in which the results o f the

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... integration experiments are found to be consistent if the He4: O16 ratio is taken as 4-0034: 16). From these masses the binding energies of the nuclei, considered as combinations of neutrons and protons, may be obtained. We find, then, that Hi2 = Hi1 + V -2-1 X 106 e-volts, Hi3 = Hx1 + 2no1 -8-1 x 106 e-volts, He23 = 2HX1 + n"1 -6-9 X 10° e-volts. The most conspicuous feature of these figures is that the binding energy of both Hx3 and He23 is considerably greater than twice that of Hx2, and the question arises as to whether this can be explained without introducing an attractive force between the neutrons in Hx3 and between the protons in He23. In this paper we attempt to answer the question by applying the variation method to calculate the binding energies of Hx3 and He23, use being made of all available information bearing on the form of the neutron-proton interaction. It is found that definite results cannot be t ' Proc. Roy. Soc.,' A, vol. 150, p. 241 (1935).