74 THE HAMILTON ASSOCIATION. 
many difficulties, and in addition he laid down three great laws, 
stated in brief as follows : 
. Every planet describes an elliptic orbit about the sun, which 
occupies one focus of each such ellipse. 
2, If a line be drawn from the sun continually to any plane 
this line will sweep over equal areas in equal times. 
3. The squares of the periodic times of the planets are pro- — 
portional to the cubes of their mean distance from the sun. 
About this time, the 17th century, was the invention of the 
telescopes, and who was the actual discoverer is not known, but 
whoever invented it, it did not penetrate into Southern [Europe till 
about 1608. Galeleo in 1610 had made observations with the tele- 
scope and had discovered the moons of jupiter. This discovery of 
course went far to confirm the Copernican theory, and with Newton’s 
immortal theory of gravitation, and Picard’s researches, the relation 
of the sun and planets became more evident and the Copernican 
theory firmly established. 
Did time permit I would like to speak of the work done by 
Laplace, Adams, Leverrier and others, but suffice to say that these, 
with Sir J. Herschel, brought Astronomy into prominence perhaps 
more than ever before, and with the introduction of better telescopes 
many new and important discoveries were made. 
The Spectroscope, an instrument of great value in the hands of 
able astronomers, reveals to us elements existing in the vapors and 
composition of the sun, etc., and stars are now known to be seen, 
some of which are much like our own sun, others differing much 
from it. Even the Nebulae have been analyzed and found to be 
stars or gas burning in space, hydrogen and nitrogen being the chief 
constituents. 
Of late years astronomical instruments have not only multiplied, 
but have been brought to a wonderful degree of perfection. 
So much for the history of Astronomy. Now let me give some 
astronomical terms frequently met with, and their explanation. 
1. Axis.—The Axis of the earth is an imaginary line passing 
through the centre, north and south ; the poles are the extremities 
of this line. 
2. Eguator.—TYhe Equator is an imaginary circle passing round 
the earth, dividing it into northern and southern hemispheres. 
