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68 THE HAMILTON ASSOCIATION. 
glass tubes from which a portion of the atmosphere had been 
exhausted, and thereby discovered many strange and wonderful 
phenomena. Wilhelm Conrad Roentgen, Professor of Physics in 
the University of Wursburg, discovered in 1895 that not only could 
the shadows of inert objects be depicted, but the tissues of the living 
human being could be examined and photographed. He placed his 
hand between the tube and a photograph plate, and beheld to his 
amazement the likeness of his bony structure. What are X-rays? 
They are Cathoid or negative rays, or in simple language a modifi- 
cation of the electric light rays. 
LIGHTNING AND INDUCE CURRENTS. 
Franklin showed that the thunder bolt of Jove and the lightning 
stroke were the same, and by his kite drew the electricity from the 
clouds. With awe and fear we watch the great phenomena of nature 
as the vivid flashes play through the stormy heavens, yet how easy it 
seems to imitate. I have shown you the electric discharge between 
the two poles of the Static, which has the appearance of miniature 
lightning, and in fact is identical. ; 
In this we have two accumulators or layden jars, one charged 
with positive electricity, the other with negative. Revolutions of 
the glass plates induce more and more electricity into the jars till 
the resistance within is greater than the resistance offered between 
the two terminals, and the opposite elements rush together, pro- 
ducing the light and noise we heard. In the atmosphere the clouds 
are layden jars or accumulators. They become polarized, that is, 
one is charged with positive electricity and the other with negative 
electricity. The clouds gather moisture as they float over ocean 
and lake. Water is a good conductor of electricity, and when the 
atmosphere and clouds have absorbed sufficient moisture to make a 
suitable passage for the electricity, the opposite elements rush 
together, causing the lightning flash and roar of thunder, producing 
condensation of the moisture, which falls in-the form of a shower. 
This lightning flash which is seen is not electricity, but a column of 
intensely heated air, which becomes luminous due to the intense 
resistance offered to the passage of the electric fluid through the air. 
We have grasped the important truth that the earth is a great 
magnet, but unlike ordinary magnets its magnetic system has four 
