6 
are due, and if the Greek astronomers had possessed the telescope 
and the pendulum, they would probably have brought this science 
to a point not actually reached till the time of Sir Isaac Newton. 
When we think of the theories and attempts to explain 
natural occurrences without the instruments of precision or the 
vast accumulation of scientific data which we now possess, we 
can only express admiration for thoughts and theories of ancient in- 
quirers. 1 might allude to the very interesting and ingenious ex- 
planation made by the ancient Egyptians of the alternation of day 
and night. It was assumed that the earth, presumably Hat, was cov- 
ered by a great dome or arch, and day was caused by the sun travel- 
ling along the inner side of the dome from sunrise to sunset; while 
from sunset to sunrise the sun on its return journey crossed the 
outside of the dome, where it was hkhh n from the earth, and the 
stars were blit holes in the dome through which the sunlight 
could be seen. This primary idea was not accepted by the Greek 
astronomers, as the theory of Hipparchus and Ptolemy (about 160 
B.C.) assumed that the sun and other bodies revolved round the 
earth as a centre. This explanation gave way to the theory pro- 
pounded by Copernicus about 1500 A.D., which is the theory 
now accepted by science. 
So with other sciences the great doctrine of the conserva- 
tion of energy and matter has become one of the basic principles 
of physics and chemistry, and the latter science has made extra- 
ordinary advances during the last few decades, and was one of 
the most important factors in the War, and made use of by both 
sides. The newer 1 science of biology is scarcely less important, 
and has revealed some of the most beautiful operations in nature. 
For instance, for long it was thought that trees and plants de- 
rived the material for their structure from the soil on which 
they grew, until the biologist showed that about 95 per cent, of 
the tree is derived, not from the soil but from the air and water, 
through the agency of sunlight acting on that wonderful material 
chlorophyll, the green substance of the leaves separating the car- 
bon from the carbonic acid gas in the air and the hydrogen from 
the water, and these two elements combining to form the wood 
structure and returning the oxygen to the air, a process which is 
reversed when we burn up the timber. The sister science of bac- 
teriology has shown how great is the part played by bacteria 
both for good and evil from a human point of view. 
The ruins of the great empires of Babylonia and Assyria 
testify to the ability of the engineers and builders. Also Persia, 
India, China, and Egypt can show that works of great magnitude 
were achieved which would even in modern times he considered 
formidable, with all our appliances and resources. Indeed, these 
ruins show the careful thought and accurate scientific knowledge 
that were brought to bear on these ancient works.. 
