THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Art. I. — An Open- Air Telescope ; by David Todd. 



"Out upon the bor:ler-land I see 

 the glimmer of new lights that wait 

 for their interpretation, and the great 

 telescopes of the future must be their 

 interpreters." — Alvan Graham Clark 

 (1893).* 



But enthusiast for the great telescope as Clark always was, 

 the advance of astronomy during the fifteen years since his 

 death has far outstripped even his sanguine expectation. 

 Already we have a number of newly-discovered variable 

 stars of the antalgol type, bright at intervals but most of the 



Fig. 1. 



Fig. 1 . 4-foot Melbourne Reflector. (Designed and built by Thomas Grubb.)f 



time very faint, and the minimum light of some of which goes 

 far beyond the visual reach of present telescopes. Ritchey's 

 marvelous photographs of nebulae and star-clusters have 



* Clark, Astron. and Astrophys., xii. 678, 1893. 

 fGrrubb, T., Phil. Trans. Eoy. Soc, clix, 127, 1869. 



Am. Jour. Sci.— Fourth Series, Vol. XXXII, No. 187. — July, 1911. 



