The Total Radiation from a Gaseous Explosion. 383 



author has not been so successful with this method — the leaf 

 occasionally adhered to the plate when so coated, and was 

 usually broken in the attempt to remove it. Other coatings 

 were tried and the method finally adopted was this : — a plate 

 of carbon was cut from one of the rods used in arc lamps, 

 and this was filed down until it was about 1*5 mm. thick; 

 its length and breadth were the same as those of the brass 

 plate. Tt was held firmly against the plate, and the ends 

 were fixed in position by a small quantity of sealing-wax. 

 This carbon surface has never given any trouble, and the 

 electroscope has worked perfectly. 



For a description of the special appliances for use with 

 this instrument in order to demonstrate various ionization 

 phenomena, the reader is referred to Prof. Zeleny's paper, 

 where ingenious simple devices for showing the photo-electric 

 effect, ionization by glowing solids, by X-rays, by radioactive 

 substances, &c, are described. As the electroscope requires no 

 attention it is particularly suitable for lecture purposes, but, 

 so far, it does not appear to have come into common use in 

 this country. 



Royal Holloway College, 

 Englefield Green. 



XL. The Total Radiation from a Gaseous Explosion. By 

 Prof. W. M. Thornton, JU.Sc, B.Eng., Armstrong College, 



Newcastle-on- Tyne* \ 



1. rMHE argument by which the lost pressure or sup- 

 X pressed heat of a gaseous explosion is made to depend 

 upon the mechanics of two colliding and cohering spheres f 

 may be extended to the case of radiation. Consider two 

 atoms of equal mass m approaching one another with equal 

 velocity v and having equal rotational and transnational 

 energies. The total energy of translation before collision is 

 mv 2 , the rotational energy lor. The vibrational energy may 

 be taken as zero at the moment before contact, for radiation 

 is not important until there is chemical combination. The 

 total loss of translational energy in collision, which is 

 equal in the case considered to j>mv 2 , is shared between 

 rotation and vibration. If equally shared, the rotational term 



* Communicated by the Author. 



t " The Lost Pressure in Gaseous Explosions, 1 ' Phil. Mag-., July 1914, 

 p. 20. 



