Report on the Solar Eclipse Expedition to Pulgaon. 53 



Erection and adjustment of Instrument. The heliostat and spectro- 

 scopes were placed on masonry piers, and a hut of bamboo matting 

 was built up round the latter. The heliostat was left in the open, 

 and, such was the dryness of the air, that it was found that a sheet 

 tied over it at night was more than sufficient to protect it from any 

 damp. 



The adjustment of the polar axis of the heliostat was carried out 

 by means of an attached theodolite in precisely the same manner as 

 has been described above in the case of the ccelostat. As it was not 

 possible to reverse the instrument when the slow motion in right 

 ascension was attached, the position of the axis when once adjusted 

 was not retested. This, however, was of little importance, as great 

 accuracy in the driving is not required for this work. 



The adjustments of the spectroscopes call for no special mention. 



Programme of Exposures. Two separate lines of work were under- 

 taken : 



(1) The recording of the spectrum of the corona using for this pur- 

 pose both spectroscopes, and giving only one exposure of as long a 

 duration as possible. 



(2) The recording of the " flash " or spectrum of the sun's limb afc 

 both the beginning and end of totality. 



For this purpose, spectroscope No. 1 only was used, the camera 

 being provided with a sliding plate, by which means a large number 

 of successive exposures could be made at short intervals. 



It was intended to begin the exposures about 10 seconds before 

 second contact, and to continue them till 7 seconds after it, and to 

 expose a similar series at third contact. 



In order to get the latter series, it was necessary to shift the image 

 on the slit, which was done by the slow motion of the heliostat, an 

 assistant being stationed at the latter, watching the sun through 

 the theodolite telescope attached to the polar axis. 



All the available time during totality, was employed in the long 

 exposure for the corona spectrum. 



The complete programme of exposures as drawn up, was as follows, 

 the expected duration of totality being 115 seconds : 



E 2 



