Photo: H. J. Shepstone. 



THE DOUBLE-SLIDE PLATE HOLDER ON YERKES 4O-INCH 

 REFRACTING TELESCOPE 



The smaller telescope at the top of the picture acts as a "finder"; the 

 field of view of the large telescope is so restricted that it is difficult to 

 recognise, as it were, the part of the heavens being surveyed. The smaller 

 telescope takes in a larger area and enables the precise object to be ex- 

 amined to be easily selected. 



MODERN DIRECT- READING SPECTROSCOPE 



(By A. Hilter. Ltd.) 



The light is brought through one telescope, is split up by the 

 prism, and the resulting spectrum is observed through the 

 other tetoecope. 



