492 



SCIENCE 



[Vol. LV, No. 1427 



Professor William D. Harkins, University of 

 Chicago. The nucleus of any complex atom may 

 be considered as a highly condensed proton- 

 electrou aggregate. Up to the present none of 

 these condensed aggregates have been found to be 

 electrically neutral (neutrons), and in most atoms 

 which exist on earth and in the meteorites each 

 electron binds two protons. Thus the composition 

 of the nuclei of most atoms may be expressed by 

 the formula (iJ^e)^, in which p represents a posi- 

 tive electron (proton), e an electron, and M is the 

 atomic number. No atomic species has been dis- 

 covered in which one electron binds more than 

 two protons. The simplest complex nucleus is that 

 of the helium atom (the alpha particle) which has 

 the formula (p^e)^ This is also the most abundant 

 group present in more complex nuclei. It was 

 shown by Harkins and Wilson in 1915 that accord- 

 ing to the special relativity theory the amount of 

 energy liberated in the formation of four grams of 

 helium from protons and electrons, that is, from 

 liydrogen, is 6.7 X 10^^ calories, or five million 

 times the energj' liberated when the same weight of 

 hydrogen unites with oxygen to form water. This 

 is about three fifths of the energy which would 

 be liberated in the complete change of 238 grains 

 of uranium into 206 grams of lead, 32 grams of 

 alpha particles, — 6N electrons (where N repre- 

 sents the avogadro number) and about 0.05 grams 

 of radiant energy. The energy which would be 

 liberated in the formation of alpha particles from 

 hydrogen is so great that it would seem that this 

 reaction should proceed at an extremely high 

 speed. That this is not the case may be due to 

 the fact that for some unknown reason one elec- 

 tron does not form a very stable union with one 

 proton, but the common ratio is two of the latter 

 to one of the former in the most stable aggregates. 

 Thus it is not improbable that four protons and 

 two electrons seldom meet at one time in such 

 relative positions as to allow the alpha particle to 

 be formed. It may be suggested that the first 

 step in the building of an alpha particle may be 

 the formation of the aggregate 2^.,^, which is sta- 

 ble with reference to aggregation, but easily 

 unites with a like particle to form the group 

 (P.,^),) or the alpha particle. According to 

 Rutherford's hypothesis the carbon nucleus con- 

 sists of four groups of the formula p e. While the 

 evidence in favor of this assumption is not spe- 

 cially convincing, there is on the other hand no 

 evidence against it. However, definite evidence 

 will be presented which proves that the alpha par- 

 ticle is the principal group concerned in the 



growth of carbon nuclei into those which are 

 heavier. The composition of any complex nucleus 

 may be expressed by the formula (.p^e)^(pe)^, 

 in which n represents the isotopic number. This 

 number varies from to 54 for known atomic 

 species, and is for most atoms. In the range 

 in which the isotopic number is small, the most 

 abundant species of atoms are those whose isotopic 

 numbers are divisible by 4, while for higher iso- 

 topic numbers the maxima of abundance are not 

 so distinct, and occur in general for the isotopic 

 numbers which are even. The most important 

 relations which should be taken into consideration 

 in showing the nature of the general system of 

 isotopes are: (1) The number of negative elec- 

 trons in most atom nuclei is even, so in general 

 the atomic weight and the isotopic number are 

 both even when the atomic number is even, and 

 are both odd when the atomic number is odd. 

 (2) As the atomic number increases the isotopie 

 number of the more stable isotopes of an element 

 also increases. This may be expressed as follows: 

 As the net positive charge on an atom nucleus 

 increases the atom becomes more unstable unless 

 at the same time the nucleus becomes more nega- 

 tive with reference to its relative content of nega- 

 tive electrons. (3) For any set of isotopes the 

 atoms become more unstable with reference to a 

 beta disintegration as the isotopic number 

 increases, and more unstable with reference to an 

 alpha particle disintegration as the isotopic num- 

 ber decreases. This relation does not specify 

 what form of disintegration will take place in any 

 special case, since this probably depends upon the 

 grouping, but it does give the relative rate for 

 any disintegration which actually does take place. 

 Obviously this relation has been tested only in 

 the case of the radioactive elements. The rela- 

 tions which exist in the general system of isotopes 

 will be presented in the form of an extensive plot 

 which exhibits a large number of relations, many 

 of them periodic, which can not be well treated 

 in au abstract. 



A theory of electric conduction in metals: 

 Professor Edwin H. Hall. 



Cooperative studies of California earth move- 

 ments: Dr. Arthur L. Day, director of the Geo- 

 physical Laboratory, Carnegie lustitutiou of 

 Washington. Recent information from astronom- 

 ical sources has indicated a northward crustal 

 movement of small magnitude in northern Cali- 

 fornia. The suggestion has been made that the 

 accumulated strains produced by such movement 

 eventually produce rupture and an elastic recoil 



