232 wells: periodic system 



I went down to the Texas flying fields about a month ago, and 

 found the cadets there splendid. They are a keen, real good lot, 

 with good discipline, and are an excellent selection of healthy 

 young men. They are all fellows who play games, or ride, or 

 enjoy some sport, and have been well chosen. But they will 

 have to be taught, even at the cost of some casualties. 



(The lecturer then showed a series of lantern slides giving views 

 of the front taken from aeroplanes, including the city of Bapaume 

 in flames, the effect of the bombardment of Guillemont at the 

 battle of the Somme, and the bombing of an aerodrome; aero- 

 plane views of England, showing the kind of information that 

 can be obtained by the aeroplane photographer concerning 

 country to be crossed by the troops; the first flying schools in 

 Wiltshire; repairs to planes and engines; the types of aeroplanes 

 and the older types of guns; and various phases of the training 

 of the flyers.) 



PHYSICS. — Note on the -periodic system of the elements. P. V. 

 Wells, Bureau of Standards. (Communicated by S. W. 

 Stratton.) 



The electron theory of atomic structure gives to the periodic 

 system a new significance. This is shown very clearly by the 

 spiral periodic table of Stoney and others as revised by Harkins 

 and Hall. The spiral form has the advantage of being in a plane 

 instead of in space, and thus of naturally representing two co- 

 ordinates, atomic number and atomic weight. 



Chancourtois, the first to discover periodicity in the properties 

 of the elements, used a helix and a period of sixteen. Newlands 

 discovered the period eight, and called his relation ''the law of 

 octaves." Mendeleef recognized both periods but considered 

 eight the fundamental period, from valence considerations. This 

 is also in harmony with the electron theory of valence. I have 

 therefore changed the spiral table given by Harkins and Hall to 

 a period of eight instead of sixteen, as is shown in figure 1 . The 

 distance from the center represents atomic weight, the elements 

 occurring in angular order of atomic number, which increases 



