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uncertain ; later than these by Berosus who first taught the Chaldean 

 learning to the Greeks, who in their turn founded the principal theories 

 of the universe that agitated the ancient world. The Pythagorcean 

 theory, 498 B.C., built on the rock of eternal unity, has stood the test 

 of ages. That the sun is the centre of our solar system, and although 

 the Ionic school founded by Thales, 600 B.C., comprises the names of 

 the greatest luminaries of ancient times, the Italic school, founded by 

 Pythagoras, taught those principles that have received the stamp of 

 Copernicus, 1543 A.D., of Kepler, 1625, of Galileo, 1643, ^"d our own 

 immortal Newton, 1727 A.D., the greatest philosopher and most pro- 

 found astronomer that ever lived. He verified the " Laws of Kepler," 

 and applied his profound analysis of the Principia, to explain the 

 harmony of revolving masses, and the balance of the planetaiy 

 system on the principles of gravity ; so that astronomy has received 

 the name of the Newtonian system, in honour of his transcendent 

 genius. Dr. Halley, Dr. Bradley (aberration of light^, Maskelyne, 

 Sir William Herschel, Brinkley, Pearson, Sir Thomas Brisbane, Sir 

 John Herschel, Sir James South, whose famous instruments, including 

 the transit instrument with which most of the valuable work has been 

 performed in the northern hemisphere, are now at work in my 

 observatory at Lancing. To my late friend Admiral Smyth, the 

 author of the " Cycle of Celestial Objects," he was indebted for some 

 of the valuable methods of observance he established with so much 

 labour. Whilst of living men of our own country, he could not pass 

 over Adams, Airey, Dawes, Hind, Lockyer, and Proctor, each of 

 whom has added something towards perfecting the profoundest 

 science with which the intellect of man can ever hope to grapple, and 

 rendered it so accurate, that now, the smallest deviations in the pre- 

 cession of the equinoxes will but add another link to the chain of 

 causation by which our own solar system is held together as part of 

 the stellar universe. 



La Place supposes that, at some very remote period, the solar 

 atmosphere extended beyond the limits of the farthest planet. The 

 sun in its primeval state resembled those nebulae described by 

 Herschel as composed of a bright nucleus, surrounded by nebulosity, 

 which, as it gradually condensed at the surface of the nucleus, ulti- 

 mately converted it into a star. Now, supposing such a condensation 

 took place, it would have been very gradual. Dynamical laws show 

 how this condensation would increase the sun's rotation, which again 



