J1ACKWARLNESS OF THE AX CI EN TS. 441 



good eyesight. In a didactic poem by Aratus, written 270 years b. a, 

 we have our earliest trustworthy account of Grecian astronomy. 

 There the Pleiades are called " t~-aT:6pot " stars traveling in seven 

 paths though according to Aratus only six stars were visible. Some 

 300 years later Ovid writes 



" Quae septem dici, sex taraen esse solent ; " ' 



while Hipparchus, in his critique of Aratus, about 150 years before 

 Ovid, expressly says that in clear, moonless nights seven stars can be 

 actually made out. Xow, Aratus lived in Macedonia, and Ovid appar- 

 ently wrote his " Fasti" at Rome, giving the finishing touches to tlie 

 work on the southern shore of the Black Sea : thus both writers lived 

 beneath a very clear sky. The fact that Hipparchus labored at Rhodes, 

 a few degrees farther south, must not be supposed to account for his hav- 

 ing seen one more star than the others, though the discrepancy between 

 the observers is all the more surprising as the group about which they 

 differed was of great importance for navigators in the then state of 

 nautical science, and was constantly under observation. This circum- 

 stance, in fact, attracted the attention of the astronomers of the time, 

 but for centuries they sought in vain for the seventh star, and offered 

 all manner of curious explanations for its supposed disappearance, one 

 of which is worthy of special mention, viz. : that this seventh star had 

 moved over to the position of the middle star in the tail of Ursa Ma- 

 jor, called by the Arabians Mizar, and that it was the little star now 

 commonly known as the Postilion and which stands close to Mizar. 

 The scholia to Homer cling to this idea of the disappearance of the 

 seventh star. Xot until the thirteenth century do we find a correct de- 

 scription of the Pleiades, in a work by the Persian astronomer Kaz- 

 vini, who apparently borrowed it from Sufi. " There are," says Kaz- 

 vini, " six stars (in the Pleiades) and in the midst of them a number 

 of dark (i. e., faint) stars;" but his observations received no attention 

 from subsequent astronomers. In vain, too, was the observation even 

 of such a man as Maestlin, Kepler's preceptor, who distinguished no 

 less than fourteen stars in the Pleiades group. Xot till after the in- 

 vention of the telescope could Sir Christopher Heyden, in 1610, write 

 as follows, showing the power of the new instrument : " I see with my 

 telescope eleven stars in the Pleiades, though never before were more 

 than seven distinguished." But how stands the case to-day ? At 

 present they who discern these eleven stars with the naked eye are 

 considered anything but prodigies ; indeed, I am acquainted with 

 persons not professional astronomers, but laymen who can make 

 out from fourteen to sixteen stars in this group. But then we are the 

 descendants of generations of men who from infancy were taught to 

 put their organs of sense to the sternest test, and to take note even 

 of the faintest sense-impressions ; our eyes have been schooled, and 



1 Said to be seven, though they number only six. 



