THE POSSIBILITIES OF INSTRUMENTAL DEVELOP- 

 MENT 1 



By George E. Hale 



Nothing is more encouraging to the scientific investigator than the 

 rapid multiplication in recent years of the possibilities of in- 

 strumental development. In astronomy the opportunities for ad- 

 vance have been vastly enlarged by the remarkable progress of 

 physics and chemistry, and the many new instruments and methods 

 ihus rendered available. To appreciate our advantages, we have 

 only to glance rapidly over the history of science and contrast present 

 possibilities with those of the past. 



The beginning of the new year, practically coinciding with the 

 annual inundation of the Nile, was fixed by observations of the helia- 

 cal rising of Sirius before 4000 B. C. Throughout their entire history 

 the Egyptian priests were astronomers, yet their sundials, water 

 clocks, and the crude " Merkhet," a measuring instrument for de- 

 termining the time from observations of stars near the meridian, 

 apparently underwent no important improvement down to the Greek 

 occupation of Egypt. The Babylonians, although much more ef- 

 fective observers than the Egyptians, have left us no instruments, 

 unless the " astrolabe " found in the palace of Assurbanipal may be 

 thus classed. The Greeks invented several instruments, which are 

 described by Ptolemy in the Almagest. Most of these consist es- 

 sentially of a graduated arc of a circle, provided with adjustable 

 sights and supported in the plane of observation. So completely did 

 these instruments embody the ingenuity of the Greeks that they were 

 adopted without important change by the Arabs, Hindus, and 

 Chinese, and served for the equipment of Tycho Brahe's great observ- 

 atory in the period of revival of the sixteenth century. Tycho de- 

 voted special attention to the improvement of instruments, which 

 he constructed in his own shops. But though spectacles had been 

 worn since the end of the thirteenth century, he little suspected the 

 great opportunity they placed within his grasp. 



The history of lenses is full of interest. It is very improbable that 

 the disk of rock crystal, oval in shape and roughly ground to a plano- 



1 Reprinted by permission from Popular Astronomy, Vol. XXXI, No. 9, November, 1923. 



187 



