1922. Langham. — Forms of Pieris napi in Co Fermanagh. 45 



15. The underside as in No. 14, but with the nervules 

 only very shghtly shaded with green ; very 

 common. 



16. The underside of hind wings bright yellow and 



nervules heavily shaded with green ; very 

 common.- 



17. The underside of hind wings decidedly pale orange 



colour and nervules heavily shaded with green. 

 I have only one taken in August, 192 1. 



Tempo, Co. Fermanagh. 



IRISH SOCIETIES. 



BELFAST NATURALISTS' FIELD CLUB. 



February 21. — J. A. S. Stendall presided. J. C. A. Brierly, M.Sc, 

 gave an interesting paper of " Radio- Activity in relation to Geology." 

 Starting with the discovery of helium in the sun's atmosphere by Sir 

 Norman Lockyer he gave the history of the observation of the photo- 

 graphic and electric effects of certain minerals ; the separation of helium 

 by Hillebrand, and its subsequent identification as helium by Lockyer 

 and Ramsay. The discovery and identification of argon by Rayleigh 

 and Ramsay, and the separation of the crude argon into argion, krypton, 

 xenon, and neon were described, and the identification of radium " emana- 

 tion " as niton was demonstrated ; these six new elements filling their 

 respective vacant spaces shown in the periodic law of Newlands and 

 ]\Iendeleeff, thus proving that no further member of this group remains 

 unknown. He then dealt with JNIons. and Madame Curie's work on 

 pitchbende and other viranium minerals and the discovery of radium, 

 afterwards describing the earlier work of Becquerel and Crookes on the 

 " Becquerel rays," demonstrating their analysis into (j^ and R and y 

 rays, and following up with the discovery of polonium and ionium, and 

 the identification of the latter as an " isotopic " form of lead. The work 

 of Rutherford and Soddy on thorium and the separation of radio-active 

 thorium X were described, and then the electric charge, mass and velocity 

 of the a particles, and the fact that the </ particles were positively 

 charged helium atoms demonstrated. The filtration and counting 

 of the a particles and the filtration, imponderability, and velocity 

 of the R rays were demonstrated, and the rate of growth and of decay 

 of radio-activity described and explained. The effect of current 

 and magnetic electricity upon the « and ^ rays and the deduc- 

 tions drawn therefrom lead to a discussion of the modern conception of 

 the constitution of the atom, and finally in considering the varying radio- 

 activity and the products thereof found in different geological strata 



