180 J. MORISON : ADDRESS — 



that it was possible for one element to be changed into another, 

 has been amply justified, though we have not yet succeeded 

 in changing lead into gold. And we can hardly consider that 

 matter is really eternal, for many things tend to show that at 

 some remote period in the far-off past it may have had 

 a beginning, and that some time in the dim and distant future, 

 when numberless aeons have come and gone, it may have an end. 

 Yet even so we cannot doubt that an infinity of universes may 

 have existed before ours came into being, and that after the 

 present Scheme of Things has at length ceased to be, an infinite 

 number of fresh creations may follow. The whole history of 

 our universe, past, present, and future, can be only a drop in the 

 ocean of eternity. 



Let us now review the various steps which led to the 

 discovery of the complexity of constitution of the atom. And 

 first let us consider what is called the ionisation of a gas. 

 Under ordinary circumstances gases are usually very slight 

 conductors of electricity, but vmder certain conditions their 

 conductivity may be greatly increased. The mere presence of 

 uranium, radium, and some other substances, make the air more 

 conductible. The air in the neighbourhood of a flame or 

 a piece of white-hot metal, is also rendered more conductible. 

 This is well shown by means of a charged electroscope. An 

 electroscope may be made by attaching a strip of gold-leaf to an 

 insulated brass column. If this apparatus be electrified or 

 charged with electricity, the electrical repulsion between two 

 bodies similarly charged causes the gold-leaf to stand out from 

 the column at an angle varying in magnitude according to the 

 amount of electrification. If such a charged electroscope be 

 brought near a lighted candle it is at once discharged and the 

 gold-leaf falls down against the column. Tliis is evidently due 

 to some change having taken place in the constitution of the 

 gases surroimding the candle which renders them more con- 

 ductible. It has been shown that this change is due to the 

 presence of electrified particles or ions emitted by the flame, 

 some charged with negative and some with positive electricity. 

 A low temperature and high pressure are favourable to the 

 production of positive ions, while a high temperature and low 

 pressure favour the foi'mation of negative ions. 



Let us take the negative ions first. They have also been 

 called electrons or corpuscles. They are inconceivably minute 

 bodies shot off from flames, from glowing metals or carbon, 

 from metals under the impact of ultra-violet light; and they 



