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THE GKEAT ECLIPSE OF AUGUST 17, 1868. 
By EICHAEB A. PEOCTOE, B.A., RE.A.S. 
AfTHOE of SATURIf AND ITS SYSTEM,” HaLF-HOFES WITH THE 
Telescope/’ etc. 
TOTAL eclipse of the sun is a phenomenon which is as 
instructive and interesting to the astronomer as it is 
impressive to the general observer. There are, indeed, few 
phenomena which have so largely influenced the progress of the 
science of astronomy as eclipses of the sun and moon. In the 
very infancy of the science, observant men were led by the 
study of eclipses to achieve the first of that long series of 
triumphs which have won for astronomy the title of the exact 
science.” Nothing but the powerful influence exerted on men’s 
minds by the obliteration of the orb of day, whilst still high 
above the horizon, could have led the ancieut Chaldean as- 
tronomers to pursue that long and laborious process of inquiry 
which resulted in their celebrated discovery of the SaroS — the 
only ancient cycle which still has a scientific value. Nor is it 
easy to over-estimate the interest of the results evolved b}^ recent 
astronomical researches from the records of eclipses which took 
place two or three thousand years ago. We see the moon’s 
motion slowly increasing, the rotation of the earth slowly di- 
minishing — effects which the observation of eclipses only could 
ever have revealed to us. In all ages of astronomy, the study 
of eclipses has had an important bearing on the science of as- 
tronomy ; but it has only been in recent times that the obser- 
vation of eclipses has led to the discovery of facts bearing upon 
the physical constitution of the great orb which sways the 
planetary system. Of late years, each successive total eclipse 
has attracted greater attention, and led to new physical dis- 
coveries. But the invention of a new instrument of research — 
the spectroscope — has led astronomers to hope yet more from 
the first great eclipse in the observation of which this instru- 
ment shall be made to take a part. Singularly enough, it 
happens that the eclipse which takes place in the present year 
will not only be interesting on this account, but will be in 
