ABSTRACT OF PROCEEDINGS. ?85 



1913. 



"On the Eelation between the Loss of Energy of 

 Cathode Rays and the lonisation produced by them." 

 By J. L. Glasson, B.A., D.Sc. 



In introducing his paper, Dr. Glasson said that Tasmania 

 exported last season between one and two hundred mil- 

 lion apples. The number seemed enormous, but spread 

 them uniformly over the w^hole of Tasmania, and they 

 would be 50ft. apart. Now, imagine the whole of Tas- 

 mania covered with apples packed as tightly as they could 

 be packed. Imagine, not a single layer only, but a pile 

 a million miles high. If she exported a million cases a 

 day all the year round, it would take her at least a hun- 

 dred thousand years to get rid of them all. The number 

 would be rei3resented by a figure with sixteen noughts at 

 the end of it. This is approximately the number of 

 atoms there are in a pin's head. And yet we have not 

 reached the limit of smallness. Each of these tiny atoms 

 has a structure as complex as the solar system. Inside it 

 there are still smaller bodies, known as electrons, whirling 

 round in their orbits at inconceivable speed. If we could 

 enlarge the atom to the size of a cathedral the electrons 

 would be represented by a few particles the size of an 

 ordinary full stop. So that the atom is really a very 

 empty thing, and the idea suggests itself that by suitable 

 means it should be possible to penetrate right through it. 

 This has actualh^ been accomplished. The discovery of 

 radium has furnished us with a projectile which can actu- 

 ally pass through solid matter without making a hole. The 

 alpha rays of radium consist of very fast moving atoms of a 

 gas known as helium. These can actually pass through 

 a sheet of paper, say, just as one solar system might be 

 imagined to sweep through another such system without 

 a single planet suffering a collision. Dr. Glasson then 

 went on to explain that occasionally collisions do occur 

 between atoms, and an electron is knocked off one of them, 

 just as we can imagine a body coming from, outside the 

 solar system and knocking the earth right out of the sys- 

 tem into free space. This process is known as ionisation. 

 The rays shot out by radium are moving with such great 

 velocity that they can penetrate a great distance through 

 a gas, occasionally colliding with the atoms which they 

 pass through. If the collisions are sufficiently severe, 

 there is a large amount of heat and light developed. So 

 that in a gas we can trace the path of one of these ionising 

 rays by the trail of glowing, mangled atoms which are 

 left behind, something like the trail of a shooting star. 



