LE ROY C. COOLEY. 35 



cision of celestial motions. These instruments suggest 

 the modern methods by which facts are discovered and 

 theories tested. 



But the ancient Greeks inherited none of these instru- 

 ments of precision. Their only observatory was an open 

 roof, and their only instrument was the naked eye. In 

 such absolute poverty of equipment, Greek astronomy 

 could be pursued, in the outset, only by the same crude 

 method which was practiced by the Chaldeans. Meas- 

 urements were impossible. The sun was said to be a foot- 

 in breadth. The distances between stars were estimated 

 in cubits. In fact, all notions of size and distance and 

 velocities were necessarily inexact, as all judgments 

 must be when based upon unaided vision. Now, the 

 Greeks saw the worthlessness of such observations. 

 They apprehended the need of mathematical exactness ; 

 and to supply it they created a new method of obser- 

 vation, by inventing instruments of measurement. 



We should, of course, expect these early inventions 

 to be, as we find they were, of the simplest form and 

 capable of yielding results far from accurate, as accuracy 

 is measured in modern times. There was the gnomon, for 

 example, which was little more than an upright staff. 

 And yet the Greek astronomer declared that Byzantium 

 and Marseilles were on the same parallel of latitude, be- 

 cause the shadows at those places have the same propor- 

 tions to the gnomon. Now, it was a long step toward 

 accuracy to abandon the simple eye-observations of the 

 altitude of the sun, and substitute therefor the measure- 

 ment of a shadow which represents that altitude, and 

 thereby compare the latitude of distant cities. The in- 

 vention of a thing so simple as the gnomon was a stride 

 in the early progress of science. A graduated circle was 

 soon afterward employed to divide the day into equal 

 portions ; and this was the prototype of the most refined 

 instruments of later days for the measurement of angles. 



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