290 



Prof. E. Rutherford on SU 



Cotton Cloths. 



July 18. Position on Right. Position on Left. ! Excess of Beading under Black 



Black Cloth. White Cloth. 



Time. No. 1184. No. 1207. No. 1184. No. 1207 



3.40 

 50 



4.0 

 10 



4.20 



so 



40 

 50 



o 

 29-1 



o 



26-9 

 27*1 



26-0 



White Cloth. 



24-4 

 24-4 



243 

 24-9 



o 

 25-8 



o 



25*5 



254 



24-6 



Black Cloth. 

 263 



Cloth, conditions being : 



26-2 



28-0 

 262 



(a) 



o 

 33 



1-7 



3-6 

 1-3 



0) 



o 

 1-4 



1-9 



(<0 



1:4 



1-9 



Aix-les-Bains, Savoie, Aug. 16, 1905. 

 P.S. — I have made some rough experiments in this place, 

 about 250 metres above the sea-level ; with two small dis- 

 mantled bath-thermometers hung side by side from a horizontal 

 bar in an open window about 12 metres above the ground. 

 The thermometers were double coated ; one with black silk, 

 the other with white cotton, round the bulb and up to about 

 17° cent, of the scale. The black was always warmer during 

 daylight. The greatest difference which 1 have hitherto 

 observed in the course of eight days was this morning, 

 37 o -6-30° = 7°-6 in bright sunshine. This was with air 

 freely circulating round the two bulbs, In a special experi- 

 ment with the two thermometers laid side by side on a slab 

 of red blotting-paper, in bright sunshine, the black-coated 

 one ran rapidly up to above 40° (the end of its scale), and 

 had to be removed to escape breakage, as it had no safety 

 space above the top of its tube. The white-coated thermometer 

 did not rise as high as 40°. Kelvin. 



XXXVII. Sloiv Transformation Products of Radium. By 

 E. Rutherford, F.E.S., Macdonald Professor of Physics , 

 McGill University, Montreal*. 



IN a previous paper (Phil. Mag. Nov. 1904) I described 

 experiments made to elucidate the changes occurring in 

 the active deposit of slow rate of transformation, which is 

 left behind on a substance after exposure to the radium 

 emanation. I showed that this active deposit contained two 

 distinct substances, called radium D and radium E, the latter 

 of which arose from the transformation of the former. The 

 product radium D gave out only /3 rays, while radium E 

 gave out only a rays. 



* Communicated by the Author. 



