72 



The observations planned were: (1) Photographs of the corona; (2) a 

 photographic search for intra-inercurial planets; (3) a photograph of the 

 spectrum of each of the flashes, and a photograph of the spectrum of the 

 corona during totality. 



For photographing the corona we used four different cameras. The 

 first was a "tintype" lens kindly loaned us by Mr. Spratt of Bloomington. 

 It has an aperture of two and one-half inches and a focal length of eight 

 inches. Three plates were exposed in this camera and on them we hoped 



Fig. I. The Polar Axis Carrying the Short Focus Cameras. 



to get long, faint coronal streamers. The second was a portrait leus of 

 the Petzval pattern, of live inches aperture and focal length twenty-eight 

 inches. This is an exceedingly good lens and gives superb definition over 

 a. small area and is very rapid. In this camera we exposed five plates, 

 varying Hie exposure from two to S4 seconds, hoping to get detail of the 

 outer corona and in the longer exposures to detect the presence of fain*' 

 streamers. The lens of the third camera is the visual objective of the old 

 telescope used by the late Professor Kirkwood and others for many col- 

 lege generations. Its diameter is three and one-half inches and its focal 



