182 Remarks o)i the Dudley Observatory 



the evening. The morning of the sixth was warm and 

 nearly cloudless. The rays of the blazing sun, acting on 

 the soil so recently saturated with plentiful rains, con- 

 stantly evaporated streams of invisible vapor, which 

 apparently condensed, at about one thousand feet above 

 the surface of the earth, into a fog, which was invisible 

 against the strongly illuminated background of the sky. 

 This fog was so dense that the Helderberg party at an 

 altitude of 1600 feet above the Observatory, were unable 

 to discern objects beneath it, and hence inferred the failure 

 of the contact observations with the thirteen inch equatorial. 



To prepare the instrument for observation, the aperture 

 was reduced to eight inches. A solar diagonal eye piece 

 by A. Clark & Sons, with plane glass reflector was 

 employed. The plane glass surfaces are inclined to 

 to each other so that the reflection from the front surface 

 alone is used. The magnifying power used in the contact 

 observations was 275 diameters. The recorded times were 

 taken from the Dent sidereal clock, whose correction and 

 rate were determined by 12 transits of stars extending 

 from a Can. Yen. (May 5. 4,) to Urs. Maj. (May 6. 4). 

 The transit was reversed for collimation on each evening. 

 The resulting correction to Dent is : 



_ 44.^7 _ 8.52 (T — 5.9) 



where T denotes the date in May expressed in fractional 

 parts of a day. 



On the night preceding the transit I had carefully 

 adjusted the instrumental focus on bright stars, anticipat- 

 ing the possibility of bad definition on the following day. 

 This proved to be a wise precaution, for the first glimpse 

 of the sun obtained through the equatorial on the morning 

 of the sixth showed the image of the sun's limb to be in a 

 state of extraordinary agitation, and that the projected 



