wind-shield. Thus the 

 requisite steadiness has 

 been secured, in spite of 

 the great height of the 

 structure. In other re- 

 spects the new tower is 

 also a decided improve- 

 ment, adding still fur- 

 ther to the sharpness of 

 the solar image during 

 the warmer hours and 

 thus increasing the du- 

 ration of the period of 

 observation, which with 

 this telescope lasts 

 throughout the day. 

 The opening up of the 

 various new fields of 

 solar research taxes the 

 capacity ot all three 

 telescopes, each of which 

 is devoted to the work 

 for which it is best 

 adapted. 



A feature of the new 

 tower telescope, which 

 is quite as important as 

 the enlarged solar image, 

 is the spectrograph,now 

 extended to a focal 

 length of 75 feet and 

 mounted in a deep well 



J 



rt 



FIG. 31. Section of 



Tower Telescope. 



