382 



SCIENCE 



[N. S. Vol. L. No. 1295 



by. competent people — it is human to err — but 

 to the want of appreciation of tbe true phys- 

 ical meaning of tbe results expressed by equa- 

 tions. A gyrostat as ordinarily considered is 

 a closed system, and its dynamical theory is 

 of a certain kind. But do away with the 

 closedness, and the dynamical theory is quite 

 a diiferent afEair. Take, as an example, the 

 case of two interlinked systems which are sep- 

 arately unstable. This compound system can 

 be made stable even in the presence of dissipa- 

 tive forces. A certain product of terms must 

 be positive, so that the roots of a certain de- 

 terminantal equation of the fourth degree may 

 all be positive. The result shows that there 

 must be angular acceleration, not retardation, 

 of the gyrostat frame. This acceleration is a 

 means of supplying energy from without to 

 the system, the energy necessary to preserve 

 in operation the functions of the system. 



I have ventured to think this stabilizing ac- 

 tion by acceleration of the compound motion 

 very important. It is lost sight of by those 

 who consider and criticize gyrostatic appli- 

 ances from the usual and erroneous point of 

 view. Also I believe that it is by analogy a 

 guide to the explanation of more complicated 

 systems in the presence of energy-dissipating 

 influences, and that the breaking down of sta- 

 bility or death of the system is due to the fact 

 that energy can no longer be supplied from 

 without in the manner prescribed for the sys- 

 tem by its constitution. 



I had just concluded this somewhat frag- 

 mentary address when the number of Nature 

 for July 24 came to hand, containing a report 

 of Sir Ernest Rutherford's lecture at the 

 Eoyal Institution on June 6. The general re- 

 sult of Sir Ernest's experiments on the col- 

 lision of a-particles with atoms of small mass 

 is, it seems to me, a discovery of great impor- 

 tance, whatever maybe its final interpretation. 

 The conclusion that "the long-range atoms 

 arising from the collision of a-particles with 

 nitrogen are not nitrogen atoms, but probably 

 charged atoms of hydrogen or atoms of mass 

 2," is of the utmost possible interest. The a- 

 particle (the helium atom, as Rutherford sup- 

 poses it to be) is extraordinarily stable in its 



constitution, and proba:bly consists of three 

 helium nuclei each of mass 4, with two at- 

 tached nuclei of hydrogen, or one attached nu- 

 cleus of mass 2. The intensely violent convul- 

 sion of the nitrogen atom produced by the 

 collision causes the attached nuclei, or nucleus, 

 to part company with the helium nuclei, and 

 the nitrogen is resolved into helium and hy- 

 drogen. 



- It seems that, in order that atoms may be 

 broken down into some primordial constitu- 

 ents, it is only necessary to strike the more 

 complex atom with the proper kind of hammer. 

 Of course, we are already familiar with the 

 fact that radio-active forces produce changes 

 that are never produced by so-called chemical 

 action; but we seem now to be beginning to 

 get a clearer notion of the rationale of radio- 

 action. It seems to me that it might be inter- 

 esting to observe whether any, or what kind 

 of, radiation is produced by the great tribula- 

 tion of the disturbed atoms and continued 

 during its dying away. If there is such radia- 

 tion, determiriations of wave lengths would be 

 of much importance in many respects. 



I may perhaps mention here that long ago, 

 when the cause of X-rays was a subject of 

 speculation, and the doctrine that mainly 

 found acceptance was that they were not light 

 waves at all, I suggested to the late Professor 

 Viriamu Jones that radiation of extremely 

 smaU wave length would be produced if atomic 

 or molecular vibration, as distinguished from 

 what in comparison might be called molar 

 vibration, could be excited. An illustration 

 that suggested itself was this : Take a vibrator 

 composed of a series of small masses with 

 spring connections. If these masses are of 

 atomic or molecular dimensions any ordinary 

 impulse or impact would leave them unaf- 

 fected, while vibrations of groups of them, 

 depending on the connections, would result. 

 But the impact on one of the masses of a 

 hammer of sufficiently small dimensions, and 

 mass would give vibrations depending on the 

 structure of the mass struck, and independent 

 of the connections, just as the bars of a xylo- 

 phone ring, while the suspended series of bars, 

 if it swings at all, does so without emitting 



