634 Dr. W. Wilson on the Discharge of 



The facts which may then be stated in favour of thunder- 

 bolts consisting mostly of ozone in active recombination 

 are : — 



1. Ozone is said to be observed on their dissipation. 



2. The gas of which they are composed is heavier than 

 air. Ozone is the only gas denser than air produced in 

 quantity under electric stress in air, as distinct from 

 streaming spark-discharge. 



3. On reaching the earth thunderbolts are frequently 

 deflected and travel horizontally as if repelled. The 

 earth's surface and ozone are both in general negatively 

 charged. 



4. The energy liberated on the transition of ozone to 

 oxygen in the volume of a fireball is sufficient to 

 account for the explosive violence with which it 

 bursts. 



5. The blue colour usually observed with it is associated 

 with the sparkless electrical discharge in air which 

 causes the production of ozone. It is also observed 

 when oxygen and hydrogen combine explosively; when 

 nitrogen is present the colour of the explosion flame is 

 yellow. 



These considerations lead one to suggest that the principal 

 though not perhaps the only constituent of thunderbolts is 

 an aggregation of ozone and partially dissociated oxygen, 

 thrown off from a negatively charged cloud by an electric 

 surge after a heavy lightning discharge. 



LXXIV. The Discharge of Positive Electricity from Hot 

 Bodies. By William Wilson, Ph.D., Assistant Lecturer 

 in Physics, University of London, King 's College*. 



IN a recent paper on the positive electrification due to 

 heated aluminium phosphate (Phil. Mag. Oct. 1910), 

 A. E. Garrett has described the effect of the presence of 

 water in the salt in temporarily increasing the positive 

 electrification produced. As I have observed a similar 

 phenomenon, I propose to publish a preliminary report of 

 research which is still in progress on the discharge of elec- 

 tricity from hot bodies. 



Experimental Arrangement. — The platinum wire, p (fig. 1), 

 formed one arm of a Wheatstone bridge arrangement, and 

 was 13 cm. in length and 0'2 mm. in diameter. The 

 adjacent arm contained a known adjustable resistance, R, of 

 thick eureka wire (immersed in paraffin oil), and a shorter 

 * Communicated bv the Author. 



