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HERE has long been a feeling which is still more or less strongly pronounced, that matter is not worthy of very serious attention from mind. Some have had the feeling that matter was the source of all our woes. Although all conscious beings are embodied in masses of matter, it was thought to be a prison-house which served mainly to quench those higher feelings to which we should aspire. The world, the flesh and the devil were all put in one class, and we were advised to have as little as possible to do with any of them.

In the meantime there have been many who have given their undivided attention to the study of the material things which surround us, and with which we must deal. The chemist and the physicist have undertaken to study the structure and the composition of matter. And the more minutely it has been studied, the more wonderful does it seem when it is considered as a specimen of engineering and architectural construction. We were formerly told that the varied forms of matter which surround us were composed of a comparatively few elementary substances, each of which was composed of particles called atoms; that these atoms were all alike for the same substance, and that they exist everywhere as far as the astronomer can penetrate, into the infinite space which the stellar systems occupy. To give some idea of the size of these atoms as determined by the army of men who in various ways have indirectly measured their dimensions, Lord Kelvin made this illustration. If a rain drop were increased in volume, until its volume equaled that of the earth, the molecules of the substance being proportionately enlarged, the water molecules would then be larger than fine shot, and not larger than cricket balls.

But during the last decade another great step has been taken. A study of radioactive substances has shown that the atom itself is a structure of wonderful complexity. A radioactive substance is one whose atoms explode into their more elementary constituents. There are a number of substances which do this, radium being the most conspicuous of the group. Each of these substances yields one kind of corpuscle or particle which is common to them all. Each atom is composed in part of minute particles having a mass of about one thousandth that of the hydrogen atom. These particles have apparently been identified as negative electricity. They constitute what Franklin called the