402 BELL SYSTEM TECHNICAL JOURNAL 



extracted and is ionized in a separate chamber; the charge-to-mass 

 ratios of its ions are determined by an especial type of deflection- 

 apparatus. Search is made for ions having the charge-to-mass ratio 

 of a singly-ionized molecule of mass about 5, such as could be a 

 molecule H^H^. Such ions occur. To discover them, however, is not 

 the same thing as to prove the existence of H\ since so far as anyone 

 can tell from their charge-to-mass ratios (as measured with the 

 accuracy attainable in these experiments) these ions might have the 

 constitution H^H^H^ — there being some of the isotope H^ in the gas. 

 How to make such discriminations is one of the major problems in the 

 analysis of the ions found in gases. In this case it happens to be known 

 that in ordinary hydrogen, the ratio of the number of triatomic to that 

 of diatomic molecular ions is proportional to the density of the gas. 

 Now in these experiments, the ratio of the number of mass-5 ions to 

 the number of mass-4 ions is the sum of two terms, one proportional 

 to the gas-density and the other independent of it. The latter term 

 is taken as the measure of the amount of H-H^, therefore of H^, in the 

 gas. A like study made with deuterium none of which had been 

 exposed to the discharge indicated a very small amount of H^ about 

 one atom in two hundred thousand of H^; the discharge enhanced 

 this ratio fortyfold in an hour. 



To return to the work at the Cavendish Laboratory: the lesser- 

 known of the two reactions which may occur when deutons meet is 

 probably described by the equation, 



,W + iH2 = 2He'^ -f ,n' + {T, - To) (2) 



and is a transmutation in the strictest sense of the word, helium as 

 well as neutrons ^ appearing out of hydrogen. I refer to it as lesser- 

 known, because although the neutrons have been observed the helium 

 nuclei have not been. This lack of evidence withholds a desirable 

 support from the equation, but does not contradict it; for on measuring 

 the momentum of the neutron, equating it to that of the hypothetical 

 He'^ nucleus and estimating the range of the latter, this range turns 

 out to be so small as to make detection difficult. We are not, however, 

 without other evidence for He^; when protons are projected against 

 lithium, particles of ranges 1.15 cm. and 0.68 cm. appear,^" and the 

 observations made with monisotopic films show that Li® is involved 

 in their origin: if we suppose 



iRi + 3Li« = 2He^ + 2Ue + {Ti - To) (3) 



'■• Harkins has suggested the name "neuton" for the element of which neutrons 

 are the ultimate particles. 



1" Kirchner has lately observed an 0.9-cni. group. 



