Page:Van Loon--The Story of Mankind.djvu/496

430 the existence of that interesting habit of falling objects which came to be known as the Law of Gravitation.

That, for the moment at least, exhausted the interest in the Heavens, and man began to study the earth. The invention of a workable microscope, (a strange and clumsy little thing,) by Anthony van Leeuwenhoek during the last half of the 17th century, gave man a chance to study the "microscopic" creatures who are responsible for so many of his ailments. It laid the foundations of the science of "bacteriology" which in the last forty years has delivered the world from a great number of diseases by discovering the tiny organisms which cause the complaint. It also allowed the geologists to make a more careful study of different rocks and of the fossils (the petrified prehistoric plants) which they found deep below the surface of the earth. These investigations convinced them that the earth must be a great deal older than was stated in the book of Genesis and in the year 1830, Sir Charles Lyell published his "Principles of Geology" which denied the story of creation as related in the Bible and gave a far more wonderful description of slow growth and gradual development.

At the same time, the Marquis de Laplace was working on a new theory of creation, which made the earth a little blotch in the nebulous sea out of which the planetary system had been formed and Bunsen and Kirchhoff, by the use of the spectroscope, were investigating the chemical composition of the stars and of our good neighbour, the sun, whose curious spots had first been noticed by Galileo.

Meanwhile after a most bitter and relentless warfare with the clerical authorities of Catholic and Protestant lands, the anatomists and physiologists had at last obtained permission to dissect bodies and to substitute a positive knowledge of our organs and their habits for the guesswork of the mediæval quack.

Within a single generation (between 1810 and 1840) more progress was made in every branch of science than in all the hundreds of thousands of years that had passed since man first looked at the stars and wondered why they were there. It