Glimpses into the world of science

Preface

T HE slow and painful growth of scientific knowledge is like that of a tree, the increased height and girth and strength of which can scarcely be traced from day to day. There are three distinct phases in this development: first, the weak seedling puts out tiny rootlets in all directions to assimilate nourish¬ ment; so in science, miscellaneous facts are collected and added to the knowledge that has gone before to form theories. Secondly, this body of knowledge gradually pushes up into the light, with layers of growth being added as small principles are perceived which correlate with others, until we have them welded into one general law. Finally we come to the branches and leaves, as these laws are worked out in fine detail, and often we see the tree flowering magnificently into the beauties, safeguards, comforts, and conveniences of this age of scientific discovery.

In this book we have tried to let the reader have a glimpse of science in all three stages of development, and also to give some idea of the infinite patience, clear, hard thinking, accuracy of experimentation, and heroic living that are by-products of the progress of scientific thought. There has been no attempt to cover all branches of science, but the chief aim has been to find articles which would arouse and hold the interest of young people. The emphasis has next been placed upon good English and upon having specialists iv PREFACE

speak for their own branches of science. The intro¬ ductions are to furnish an enlightening background for the articles themselves.

Thanks are due the many friends who gave us valu¬ able suggestions and who helped in many other ways.

Mary Geisler Phillips William Henry Geisler

Contents

Preface .iii

Galileo Galilei, Founder of Experimental

Science. Ivor B. Hart . 1

Chapter II. The Microscopic Examination of the Solid Particles Found in the Atmosphere

My first care was to find a method which should per¬ mit of collecting the solid particles that float in the air and of studying them under the miseroscope. It was first necessary to remove if possible the objections held by the partisans of spontaneous generation against the ancient hypothesis of the aerial dissemination of germs. . . .

The method which I have used to collect and examine the dusts suspended in the air is very simple; it consists in filtering a known volume of air through gun cot¬ ton, which is soluble in a mixture of alcohol and ether. The solid particles collect on the fibers of the cotton. The cotton is then treated with its solvent, and after a time all the solid particles fall to the bottom of the liquid; they are washed several times and transferred to the stage of the microscope, where they are easily ex¬ amined. . . .

These simple manipulations allow one to observe that ordinary air always contains a variable number of cor¬ puscles 4 whose form and structure show them to be of organic nature. In size they vary from the smallest diameters up to 1/100 to 1.5/100 of a millimeter, or more. Some are perfectly spherical, others oval. Their outlines are more or less sharply defined. Some are quite transparent, but others have a granular substance and are opaque. Those which are transparent with clearly defined outlines are so much like the spores of common molds that the cleverest microscopist could not distinguish between them. That is all that one can say, just as one can only affirm that among the others there 4 Small bodies.

are some which resemble encysted 5 infusoria or the globules which are regarded as the eggs of these minute creatures. . . .

I found that a little wad of cotton, thus exposed for twenty-four hours in the summer after a spell of fine weather to a current of one liter of air a minute from the Hue d’Ulm, collects several thousands of organized corpuscles. The number varies indefinitely with the state of the atmosphere — before or after rain, in still or windy weather, by day or by night, near the ground or at some distance from it. . . .