Photograph from Yerkes Observatory 



THE LARGEST REFRACTING INSTRUMENT IN THE WORLD: THE YERKES 



40-INCH TELESCOPE 



This "big gun" of the astronomical world is a Brobdingnagian eye. 40,000 times as power- 

 ful as the human optic. A human eye to be as powerful as it is would have to be 25 feet in 

 diameter, and the man who could possess such an eye would have to be 1,200 feet high (see 

 also page 158). 



161 



