196 Sir W. and Lady Huggins. On the Spectrum [July 17, 



" On the Spectrum of the Spontaneous Luminous Eadiation of 

 Kadium at Ordinary Temperatures." By Sir WILLIAM 

 HUGGINS, K.C.B., O.M., D.C.L., Pres.K.S., and Lady HUGGINS. 

 Keceived July 17, 1903. 



[PLATE 8.] 



The discovery of an element possessing such remarkahle and novel 

 properties as radium, which in its separate and distinct form as a new 

 chemical element we owe to the researches of Professor and 

 Mdme. Curie, has already thrown many beams of suggestive light into 

 the very obscure regions of the constitution of matter. In radium we 

 have a body which appears to be spontaneously and without ceasing 

 giving off energy in several forms. According to Professor Rutherford,* 

 following upon the work of Becquerel, M. and Mdme. Curie, and others, 

 the emanations going off from radium are at least of three kinds. 

 First, an emanation of heavy corpuscles, larger in mass than the 

 hydrogen atom, moving with a high velocity, and carrying a positive 

 charge ; secondly of negatively charged electrons which form a power- 

 ful and penetrating cathode emanation;! and further, of a radio- 

 activity which diffuses from the radium as if gaseous in its nature. 

 In addition, M. and Mdme. Curie have found that radium spontaneously 

 maintains a temperature about 1'50 C. above the surrounding tem- 

 perature, and therefore emits heat radiations of wave-lengths falling 

 within the infra-red part of the spectrum. 



Now, in addition to these forms of radiant energy, the glowing of 

 radium in the dark shows that it emits a luminous radiation spontane- 

 ously at ordinary temperatures. It appeared to us probable that in this 

 glow we had not 10 do with either phosphorescence or fluorescence as 

 usually understood, but with an independent and continuous radiation 

 set up by those more active molecules which are supposed, in conse- 

 quence of a condition of internal instability, to be the source of all 

 the phenomena of radioactivity, and which can scarcely fail them- 

 selves to be violently agitated, in connection with disruptive molecular 

 changes especially the flinging off of the heavy corpuscles during 

 which, part of the energy stored up within the molecule is liberated 

 in the kinetic form. 



* < Phil. Mag.,' April and May. 



t As an illustration of the penetrative power of the radio-active effects of pure 

 radium bromide, the following experience may be recorded here. About 1 centi- 

 gramme of radium bromide (Buchler & Co., Brunswick) had been placed in an 

 upper drawer of my writing table, while in a lower cupboard of the same table was 

 a store of photographic plates. After a week or two, all the plates, in boxes lying 

 upon each other three or four deep, were found to be as completely fogged as if they 

 had been exposed to light. 



