BACKWARDNESS OF THE ANCIENTS. 443 



not altogether escape his means of observation. "It appears," he 

 cautiously observes, "as if the pole-star had a motion [round the 

 pole] like the rest of the stars." 



Again, is it not amazing that for thousands of years mankind 

 should have been in presence of so frequent a phenomenon as the 

 zodiacal light a phenomenon which in southern latitudes is spe- 

 cially impressive without considering it to be worthy of mention, 

 or rather, let us say, without seeing it, until Childrey, in the middle 

 of the seventeenth century, discovered it, if we may so speak ? So, 

 too, may it excite our wonder, to think that the earliest definite men- 

 tion of the noteworthy phenomena (easily visible with the naked eye) 

 attending a total eclipse of the sun dates only from the year 1706, 

 that is to say, a period of time full one hundred years subsequent to 

 the invention of the telescope. 



Thus the ancients were deficient in even the most elementary 

 powers of observation. The simple but truthful noting of what is 

 perceived by the senses is the prerogative of our time. But what 

 of the restless spirit of speculation with which Schiller taxes the 

 ancients ? 



Here permit me to recall anew to your memories, by an instance 

 taken from the history of astronomy, thoughts which oftentimes, 

 perhaps, have occurred to us all. Plutarch's dialogue on "The 

 Visage that is seen in the Moon's Disk " has ever been regarded as 

 containing the sum and substance of all man's notions and knowledge 

 of our satellite down to the period when it was written. The very 

 title is provocative of mirth to us, the children of the modern time. 

 The Visage in the Moon ! Nowadays it only suggests to the poet 

 and the artist satirical ideas : in olden times it was the starting-point 

 of profound meditations, which were held not to be unworthy of 

 being attributed to the most famous philosophers and mathematicians 

 of the day. The author first in all earnestness demonstrates the ab- 

 surdity of the opinion which asserts the figure appearing in the moon 

 to be nothing else but an optical illusion arising from the visual sense 

 being dazzled by the brightness of the moon's disk. Next we have a 

 lengthy refutation of another opinion, which says that the visage in 

 the moon is the reflection of our ocean. Among other reasons given 

 to show the erroneousness of this opinion is this, that there is only 

 one ocean, and that, if the visage in the moon were a reflection of it, 

 then the ocean must be made up of parts separated from one another 

 by isthmuses and continents ! The third opinion combated by Plu- 

 tarch is to the effect that the moon is a mixture of air and of a mild 

 kind of fire ; as sometimes during a perfect calm the surface of a body 

 of water becomes ruffled a thing itself to be demonstrated so too 

 does the air assume a blackish color: thus is explained the appearance 

 as of a human face in the moon. The hypothesis of the Stoics, who 

 affirmed the moon to be a globe of fire, on the surface of which rests 



