Show weekly guide to science e by permission of POPULAR SCIENCE MONTHLY CHAPTER HI WHAT THINGS ARC SLIDE MADE or OF twenty five alve years ago when madame curio and her husband discovered radium they began a series ot of scientific re bearch on all which many men have worked and which have given us ua a much gre greater ter knowledge ol of the r real e al nature of matter than men ever dreamed ot of oe be tore fare wo we have learned that tile the atoms which wo we used to think ot of as the smallest parts ol of matter and as indivisible are not really indivisible at all indeed they are very complicated things with at least two different kinds or of parts inside them small as they are millions ol of them could stand on the point ot of a needle needie we find inside them a makeup make up much like that ot of the solar system at the center of each atom Is a very tiny particle which scientists call the nucleus it corresponds to the s sun u n in the solar system A round around this n nucleus u c leus there revolve a large number ot of other tiny particles called electrons they correspond to the planets during the past live alve years this very tiny ny world inside the atom lifts has yielded some ot of the most astonishing discoveries ever made by science further researches are proceeding with unexampled speed you will be reading many marvelous ous facts about atoms in the scientific news ot of the next few years CAN WE S SEE EE ATOMS WITH will A microscope I 1 no they are tar far too small it takes more than two hundred million hydrogen atoms laid side to side to make up one inch the other kinds ot of atoms are only 0 a little larger than this more than fifty ot of atoms can crowd to gether on the head ot of an ordinary pin if this many people were marching in a parade and it 1 they marched night and day at a fast walk fifty abreast it would take over seven thousand years tor for all ot of them to pass by WHAT IS TIIE THE difference BETWEEN ATOMS AND all substances are composed of exceedingly minute particles all alike and in rapid motion called molecules their speed may be as high as a mile a second each molecule may be a single atom a few atoms ot of the same kind or an association ot of groups ot of atoms ot of different kinds WHAT ARE rnO PROTONS TONS particles ot of positive electricity which I 1 repel each other but attract electrons they revolve like planets inside ol of the nuclei ot at atoms where they are associated roc socia ted with halt half as many electrons as there are protons A proton has a mass 1845 times as great as that ot of an electron HOW MANY DIFFERENT CHEMICAL ELE ELEMENTS MENTS ARE AKE THERE eighty six are now known |