86 THE EVOLFTION OF SCIENCE. 



Even by the Greeks themselves it was developed into 

 the quadrant, essentially the same as the modern instru- 

 ment with this name. Armils, to mark with precision 

 the time of the equinoxes and solstices, and the astro- 

 labe, for measurements referred to the ecliptic, were also 

 inventions of the early Greeks. 



This introduction of the idea and the means of meas- 

 urement was the first step in the actual progress of 

 scientific astronomy. In fact, we may say that it was 

 the birth of the only philosophic, and, therefore, fruitful 

 method of attacking science in any of its provinces. 



Without the instrumental means to make obser- 

 vations, and to measure phenomena, the knowledge of 

 nature can be nothing more than the common every-day 

 conceptions of things applied to the common and every- 

 day wants of life, inspiring nothing but vague if not 

 superstitious notions of the laws of nature. But by 

 the use of instruments the limitations of the organs of 

 sense are overstepped ; their inaccuracies are detected 

 and corrected ; the catalogue of facts is extended ; the 

 weight and value of each is determined; and the judg- 

 ment is, in this way, furnished with appropriate data 

 out of which to construct and by which to test its hy- 

 potheses. 



The sagacity of Thales led him to announce some new 

 truths, which, being destitute of instruments, he was not 

 able to demonstrate, nor to separate by a distinct line 

 from much that was false. But, in the course of time, 

 the dial, the astrolabe, the armil, and the quadrant, were 

 invented. Then came Hipparchus, sometimes called the 

 prince of Greek astronomers, who measured the obliquity 

 of the ecliptic ; who determined the length of the year 

 to within twelve seconds of the truth ; who discovered 

 the excentricity of the lunar and solar orbits, and the 

 inequality in the lengths of the solar day, which makes 

 it impossible for the best-regulated clock to keep true 



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