d the Batt

r mouldy manuscripts and asked, "What do the great philosophers say ought to happen?" instead of looking at nature and asking, "What does happen?" And when a man arose

dent of history that the brunt of the attack fell upon a man born in Italy in 1564, and that the battle was fou

er, who was one of the noted musicians of his day. His skill in drawing was such that noted artists submitted their work to him for criticism. He wrote essa

fered little prospect of profitable work, he took up the

question by referring to what the ancient philosophers said. Galileo could not endure such slavish submission to authority. So st

father, learning of this, consented to his becoming a mathematician.

ndulum

bronze lamp which had been drawn back for lighting. Timing its swinging by means of his pulse, the only timepiece in his possession, he found that the time of one swing remained the same, though the l

ILEO'S PEN

nd, which is not s

tudies. The writings of Archimedes were his favorite study. With Archimedes' famous experiment on King Hiero's crown as a starting-point, he disco

nd of that time he was appointed professor of mathematics in the University of Pisa at the magnificent salary of sixty scudi (about sixty-three dollars) per year. "But any

periment wit

he one-pound shot. But the assembled company of professors and students saw the two shot start together, fall together, and strike the ground at the same instant, and still refused to believe their own eyes. They continued to affirm that a weight of ten pounds would reach t

by a nephew of the Grand Duke for the purpose of cleaning harbors. Galileo plainly said that the machine was worthless. It was tried, and his opinion proved true. B

and two sisters. In his distress he sought help from a friend, and secured an appointment as professor of mathematics in the University of

in most cases of mathematical instruments and is used in certain kinds of drawing. He a

N AIR TH

outside forces the Water up the tube. When the air in the bulb

the new star must lie among the most distant of the heavenly bodies, and this fact did not agree with Aristotle's view that the heavens are perfect, and therefore never change. A heated controversy followed, an

Tele

f two of the lenses were placed in a certain position objects seen through them appeared much nearer. Galileo, learning of this, set to work to construct a spy-glass, applying his knowledge of light. In one day he had const

s. He was the first to apply the telescope to the study of the heavenly bodies. The most startl

citement was intense. Poets chanted the praise of Galileo. A public fête was held in his honor. One of his pupils was imprisoned in the tower of San Marco, where he had gone to make

o's St

o did. Others claimed that his discoveries were false, that their only use was to gratify Galileo's vanity and thirst for

ore decided to leave Padua, and secured an appointment as mathematician and philosopher to the Grand Duke of Tuscany. This appointment too

de were arrayed those who said that men should always believe as the ancient writers did; on the other, those who said men should think for themselves. In the first party were most of

orted the incident to Galileo, and he replied to the arguments of his opponents in a letter which was made public. No doubt the sting of his sarcasm made his enemies more bitter. He admitted that the Scriptures cannot lie or err, but this, he

ck, was used by the combined forces to break the power of Galileo's reasoning. He went to Rome to make his defence, but

recalled that some years before he had so arranged a telescope that he had seen flies which he said looked as big as a lamb, and were cover

granted. Before he recovered, however, the summons was made imperative. He must go to Rome, or be carried in irons. He went in a litter, carried by servants of the Grand Duke. In Rome he was to appear before the Inquisition. There he was treated with a consideration never before accorded to a prisoner of the Inquisition. Nor was

renounced his "errors and heresies," and, with his hand on th

life-work, nothing could quench his devotion to science. In these last years, he published a new book

ver a machine is at work, a man or a horse, or some other power, is at work upon the

i and the

him that no pump would do better. This led Torricelli, one of Galileo's pupils, to the discovery of the barometer. Men had said that water rises in a pump because nature abhor

ry. He allowed the tube to stand, and saw that the height of the mercury changed. This he believed was because the air-pressure changed. Wind, Torricelli said, is caused by a differ

RICELLI'S

ericke and

hirteen years. The Swedish King, Gustavus Adolphus, had landed in Germany, and was winning victory after victory over the imperial troops. Magdeburg had enter

arrive. While Gustavus was on his way to the rescue, Magdeburg was taken by storm, and the most horrible scene of the Thirty Years' War was enacted. Tilly gave up the city to plunder, and his soldiers without mercy kil

y was again before the walls, and Magdeburg, then in the possession of the Swedes, was compelled to yield to the

nue his studies. He made the first air-pump, and with it pe

periments before the Emperor. The most striking of these experiments he performed with two hollow copper hemispheres about a foot in diameter, fitted closely toget

pulley, and a large number of men applied their strength to the rope to hold the piston in place. When the air was taken out of the cylinder, the piston was forced do

UERICKE'

m the ground b

was filled with water, and the top projected above the roof of the house. On the water in the tube he placed a wooden image of a man. In fair weather the image would be

ICKE'S WATE

housetop. When a storm was approaching the

hur turning on a wooden axle. He observed that when the dry hand was held against

d the Pressure

ir-pump without applying heat. It is now well known that water when boiling on a high mountain is not so hot as when boiling down in the valley. This is because the air-p

pneumatic tire of the bicycle or automobile. Boyle found that the more air is compressed the greater is its press

the Hydra

t of the mountain, and the other was carried to the summit, about three thousand feet high. The mercury in the second barometer then stood more than three inches lower than at first. As the barometer was carried down the mountain the mercury slowly rose until, at the foot, it stood at the same height as at first. The party stopped abou

–A LIF

e in the pump. The air can do this only when the plunger is at wor

very nine hundred feet of elevation the mercury is lowered about one inch. In this way the height of a mountain can be measured, and a man in a balloon o

with his own hand, he could move the earth if only he had a place to stand. Pascal could so arrange his machine that a man pressing with a force of a hun

IMPLE HYDR

ght holds up a

of one square inch, and the other has an area of one hundred square inches, then every pound of pressure on the small piston causes a hundred pounds of pressure on the large piston. A hundred pounds on the small piston would lift a weight of ten thousand pounds on the large piston. But we can see that the lar

AN HYDRAULI

the machine. The arrows show the direction in which the liquid is forced by the a

ULIC PRESS WITH

wt

ay the boy above him in class gave him a kick in the stomach. This roused him and, to avenge the insult, he applied himself to study an

to these kites and fly them on dark nights, to the delight of his companions and the dismay of the superstitious country people, who mistook them for comets portending some great calamity. He made a toy mill to be run by

ng. The sheep went astray, and the cattle trod down the corn while he was perusing a book or working with some machine of his own construction

vit

one day alone in the garden thinking of the wonderful power which causes all bodies to fall toward the earth. The same power, he thought, which causes an apple to fall to the ground causes bodies to fall on the tops of the highest mountains and in

k. When this was done by one of his friends, it was found that Newton's thought was correct-that the force of gravitation which causes bodies to fall at the earth's surface is the same a

in Su

scopes. His first experiment was to admit sunlight into a darkened room through a circular hole in the shutter, and allow this beam of light to pass through

ere separated by the glass prism. In the same way the colors of sunlight are separated by raindrops to form a rainbow

s and flowers would have a dull, leaden hue, and the human countenance would have the appearance of a pencil-sketch or a photographic picture. The rainbow itself would

'S EXPERIMENT

e rainbow. The seven colors are: violet,

scope in which a curved mirror was used in place of a lens. He made s

James II. to be no longer King of England and tendered the crow

the Mint. It was his duty to superintend the recoining of the money of England, which ha

im that it came from a great duchess. Newton replied: "Tell the lady that if she were here herself, and had made

discovered. He said of himself: "I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the sea-shore and di